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1.
Med Sci Educ ; 34(4): 909-913, 2024 Aug.
Article in English | MEDLINE | ID: mdl-39099853

ABSTRACT

Collaborative methods for learning such as team-based learning, case-based learning, and problem-based learning have become leading methods for active learning within the field of health professions education. Critical thinking and exposure to diverse perspectives within a group are highlighted as important benefits of team-based learning. However, without consideration of the potential socioemotional, behavioral, and team dynamic challenges associated with this format of learning, the tenets which support a welcoming learning community can begin to deteriorate. In this essay, authors highlight the core concepts of growth mindset, psychological safety, and culturally responsive pedagogy within a framework of 1) what learners should know and 2) what educators can do, to co-create an inclusive collaborative learning experience.

3.
BMC Med Educ ; 23(1): 959, 2023 Dec 14.
Article in English | MEDLINE | ID: mdl-38098014

ABSTRACT

BACKGROUND: Medical educators seek innovative ways to engage learners efficiently and effectively. Gamification has been explored as one way to accomplish this feat; however, questions remain about which contexts gamification would be most useful. Time constraints and student interest present major barriers for teaching laboratory medicine to students. This study aims to compare two versions of an interactive online module, one gamified and one not, for teaching laboratory medicine concepts to pre-clinical medical students. METHODS: First-year medical students reviewed either a gamified or non-gamified version of an interactive online module in preparation for an in-person flipped classroom session on Laboratory Medicine. Learning theory guided the design of the modules and both contained identical content, objectives, and structure. The "gamified" module included the additional elements of personalization, progress meters, points, badges, and story/role play. After reviewing the module, students completed an anonymous knowledge check and optional survey. RESULTS: One hundred seventy-one students completed the post module knowledge check as assigned (82 gamified, 89 non-gamified). Knowledge check scores were higher for the students who reviewed the gamified module (p < 0.02), corresponding to an effect size of 0.4 for the gamified module. Eighty-one students completed optional post-module surveys (46 gamified, 35 non-gamified). Instructional efficiency was calculated using task difficulty questions and knowledge check scores, and the resulting instructional efficiency was higher for the gamified module. There was no significant difference in the student-reported time required to complete the modules. Additionally, both versions of the module were well received and led to positive ratings related to motivation and confidence. Finally, examination of open-ended survey results suggested that the addition of game elements added value to the gamified module and enhanced engagement and enjoyment. CONCLUSIONS: In this setting, the addition of gamification to an interactive online module enhanced learning outcome, instructional efficiency, student engagement and enjoyment. These results should inspire further exploration of gamification for teaching Laboratory Medicine concepts to pre-clinical medical students.


Subject(s)
Medicine , Students, Medical , Humans , United States , Laboratories, Clinical , Schools, Medical , Learning
4.
BMC Med Educ ; 23(1): 345, 2023 May 17.
Article in English | MEDLINE | ID: mdl-37198639

ABSTRACT

BACKGROUND: Preclinical medical education is content-dense and time-constrained. Flipped classroom approaches promote durable learning, but challenges with unsatisfactory student preparation and high workload remain. Cognitive load theory defines instructional design as "efficient" if learners can master the presented concepts without cognitive overload. We created a PReparatory Evaluation Process (PREP) to systematically assess and measure improvement in the cognitive-load efficiency of preparatory materials and impact on study time (time-efficiency). METHODS: We conducted this study in a flipped, multidisciplinary course for ~ 170 first year students at Harvard Medical School using a naturalistic post-test design. For each flipped session (n = 97), we assessed cognitive load and preparatory study time by administering a 3-item PREP survey embedded within a short subject-matter quiz students completed before class. Over three years (2017-2019), we evaluated cognitive load- and time- based efficiency to guide iterative revisions of the materials by content experts. The ability of PREP to detect changes to the instructional design (sensitivity) was validated through a manual audit of the materials. RESULTS: The average survey response rate was ≥ 94%. Content expertise was not required to interpret PREP data. Initially students did not necessarily allocate the most study time to the most difficult content. Over time, the iterative changes in instructional design increased the cognitive load- and time-based efficiency of preparatory materials with large effect sizes (p < .01). Furthermore, this increased the overall alignment of cognitive load with study time: students allocated more time to difficult content away from more familiar, less difficult content without increasing workload overall. CONCLUSIONS: Cognitive load and time constraints are important parameters to consider when designing curricula. The PREP process is learner-centered, grounded in educational theory, and works independently of content knowledge. It can provide rich and actionable insights into instructional design of flipped classes not captured by traditional satisfaction-based evaluations.


Subject(s)
Curriculum , Education, Medical , Humans , Learning , Surveys and Questionnaires , Cognition , Problem-Based Learning
5.
BMC Med Educ ; 22(1): 821, 2022 Nov 29.
Article in English | MEDLINE | ID: mdl-36447223

ABSTRACT

BACKGROUND: Students with developed self-regulated learning (SRL) skills demonstrate an ability to set individualized educational goals, select optimal learning strategies for reaching these goals, and reflect on overall progress. The primary aims of this study were to investigate first-year medical students' perceived utility of a self-regulated learning-informed intervention and to assess the impact of its implementation on students' intended use of SRL throughout medical school. METHODS: A two-part educational intervention focused on SRL skill development was carried out at Harvard Medical School during the start of the 2021 academic year. For the first component of the intervention, 169 first-year medical students engaged in an interactive class session structured around SRL concept videos, a brief lecture, small group discussions and individual reflection. Students completed pre- and post-intervention surveys which inquired about learners' current and anticipated application of SRL skills. During the second component of the intervention, 15 first-year medical students participated in a set of one-on-one academic SRL coaching sessions. All coaching participants completed follow-up semi-structured interviews. RESULTS: A statistically significant increase was observed between students' use of skills in all domains of self-regulated learning prior to the intervention and their anticipated use of these skills following the intervention. Prior to the intervention, 60.1% (n = 92) of students reported utilizing evidence-based learning strategies, compared to 92.8% (n = 142) of students (p < 0.001) who anticipated applying this SRL skills at the completion of the classroom session. Six core themes emerged from qualitative analysis of the post-intervention survey including learning plan development, accountability and progress tracking, goals for growth, engagement through active learning, routine reflection, and adapting to the curriculum. CONCLUSIONS: Both classroom-based learning sessions and one-on-one academic coaching programs are feasible approaches for encouraging the use of self-regulated learning techniques in the preclinical setting.


Subject(s)
Mentoring , Students, Medical , Humans , Schools, Medical , Learning , Problem-Based Learning
6.
BMC Med Educ ; 22(1): 423, 2022 Jun 02.
Article in English | MEDLINE | ID: mdl-35655160

ABSTRACT

PURPOSE: The disruption of undergraduate medical education (UME) by the COVID-19 pandemic has sparked rapid, real-time adjustments by medical educators and students. While much is known about online teaching in general, little guidance is available to medical educators on how to adapt courses not originally designed for the online environment. To guide our faculty in this transition we conducted a needs assessment of students enrolled in virtual courses across all 4 years of UME training. METHODS: Using a mixed-methods approach, we conducted a single-institution virtual learning needs assessment in May and June of 2020. We developed and disseminated a survey to assess student experiences with virtual learning. We conducted quantitative and qualitative analysis of responses (n = 255 or 39%) to identify emergent themes. RESULTS: We identified six interdependent themes that need to be met for medical students to fully reach their learning potential: access to stable internet and quiet study spaces, flexible course design with asynchronous, self-paced components, clear expectations for engagement with content and each other, a sense of connectedness with faculty and peers, synchronous classes that maximize interactivity, and assessments that foster a sense of learning over performance. Interpersonal relationships with faculty and peers affected students' sense of learning more than any other factor. CONCLUSIONS: Based on our findings we propose a hierarchy of needs for virtual learning that provides guidance on adapting existing medical school courses to the remote setting and overcoming common challenges. We highlight opportunities for how virtual elements may enrich in-person courses going forward, including in the clinical setting. Although the solutions required to meet the threshold of need at each level may differ based on the context, attending to these same fundamental needs can be extrapolated and applied to learners across a range of environments beyond the virtual.


Subject(s)
COVID-19 , Education, Medical, Undergraduate , Students, Medical , COVID-19/epidemiology , Humans , Pandemics , Surveys and Questionnaires
7.
Acad Med ; 97(10): 1467-1473, 2022 10 01.
Article in English | MEDLINE | ID: mdl-35108233

ABSTRACT

Scientific research has been changing medical practice at an increasing pace. To keep up with this change, physicians of the future will need to be lifelong learners with the skills to engage with emerging science and translate it into clinical care. How medical schools can best prepare students for ongoing scientific change remains unclear. Adding to the challenge is reduced time allocated to basic science in curricula and rapid expansion of relevant scientific fields. A return to science with greater depth after clinical clerkships has been suggested, although few schools have adopted such curricula and implementation can present challenges. The authors describe an innovation at Harvard Medical School, the Advanced Integrated Science Courses (AISCs), which are taken after core clerkships. Students are required to take 2 such courses, which are offered in a variety of topics. Rather than factual content, the learning objectives are a set of generalizable skills to enable students to critically evaluate emerging research and its relationship to medical practice. Making these generalizable skills the defining principle of the courses has several important advantages: it allows standardization of acquired skills to be combined with diverse course topics ranging from basic to translational and population sciences; students can choose courses and projects aligned with their interests, thereby enhancing engagement, curiosity, and career relevance; schools can tailor course offerings to the interests of local faculty; and the generalizable skills delineate a unique purpose of these courses within the overall medical school curriculum. For the 3 years AISCs have been offered, students rated the courses highly and reported learning the intended skill set effectively. The AISC concept addresses the challenge of preparing students for this era of rapidly expanding science and should be readily adaptable to other medical schools.


Subject(s)
Clinical Clerkship , Curriculum , Humans , Learning , Schools, Medical
8.
Med Sci Educ ; 31(6): 1779-1788, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34956697

ABSTRACT

Teamwork skills are recognized as a core competency of physicians. To more effectively prepare trainees for the demands of their future work, medical educators are increasingly turning to group-based instructional formats. We employ case-based collaborative learning (CBCL) - a format which requires daily in-class discussion and collaboration in assigned small groups. While students overwhelmingly embraced CBCL as stimulating and thought-provoking, some students reported that social dynamics among group members adversely impacted their experience. Using mixed methods, we demonstrate that a short intervention that asked students to discuss how they can best learn together improved small group dynamics, and promoted psychological safety among peers. Importantly, no specific instruction in team work was required, students overall had a clear understanding how they could improve, but they did not know how to start this conversation with each other. To promote team learning, we propose that educators emphasize students' accountability to their peers' learning in addition to their own, and devote some time in class for teams to reflect and discuss how to improve learning with each other. Our observations are of interest to anyone frequently relying on group work without peer assessment or formal feedback on group performance.

10.
Acad Med ; 95(11): 1687-1695, 2020 11.
Article in English | MEDLINE | ID: mdl-32134787

ABSTRACT

As the U.S. health care system changes and technology alters how doctors work and learn, medical schools and their faculty are compelled to modify their curricula and teaching methods. In this article, educational leaders and key faculty describe how the Pathways curriculum was conceived, designed, and implemented at Harvard Medical School. Faculty were committed to the principle that educators should focus on how students learn and their ability to apply what they learn in the evaluation and care of patients. Using the best evidence from the cognitive sciences about adult learning, they made major changes in the pedagogical approach employed in the classroom and clinic. The curriculum was built upon 4 foundational principles: to enhance critical thinking and provide developmentally appropriate content; to ensure both horizontal integration between courses and vertical integration between phases of the curriculum; to engage learners, foster curiosity, and reinforce the importance of student ownership and responsibility for their learning; and to support students' transformation to a professional dedicated to the care of their patients and to their obligations for lifelong, self-directed learning.The practice of medicine is rapidly evolving and will undoubtedly change in multiple ways over the career of a physician. By emphasizing personal responsibility, professionalism, and thinking skills over content transfer, the authors believe this curriculum will prepare students not only for the first day of practice but also for an uncertain future in the biological sciences, health and disease, and the nation's health care system, which they will encounter in the decades to come.


Subject(s)
Clinical Competence , Curriculum , Education, Medical, Undergraduate , Problem-Based Learning , Stakeholder Participation , Thinking , Educational Measurement , Faculty, Medical , Humans , Needs Assessment , Teaching
11.
Med Teach ; 39(6): 653-659, 2017 Jun.
Article in English | MEDLINE | ID: mdl-28332912

ABSTRACT

Increasingly over the past decade, faculty in medical and graduate schools have received requests from digital millennial learners for concise faculty-made educational videos. At our institution, over the past couple of years alone, several hundred educational videos have been created by faculty who teach in a flipped-classroom setting of the pre-clinical medical school curriculum. Despite the appeal and potential learning benefits of digital chalk-talk videos first popularized by Khan Academy, we have observed that the conceptual and technological barriers for creating chalk-talk videos can be high for faculty. To this end, this tips article offers an easy-to-follow 12-step conceptual framework to guide at-home production of chalk-talk educational videos.


Subject(s)
Calcium Carbonate , Curriculum , Videotape Recording , Humans , Learning , Schools, Medical
12.
EMBO J ; 33(10): 1159-76, 2014 May 16.
Article in English | MEDLINE | ID: mdl-24811749

ABSTRACT

Degradation rates of most proteins in eukaryotic cells are determined by their rates of ubiquitination. However, possible regulation of the proteasome's capacity to degrade ubiquitinated proteins has received little attention, although proteasome inhibitors are widely used in research and cancer treatment. We show here that mammalian 26S proteasomes have five associated ubiquitin ligases and that multiple proteasome subunits are ubiquitinated in cells, especially the ubiquitin receptor subunit, Rpn13. When proteolysis is even partially inhibited in cells or purified 26S proteasomes with various inhibitors, Rpn13 becomes extensively and selectively poly-ubiquitinated by the proteasome-associated ubiquitin ligase, Ube3c/Hul5. This modification also occurs in cells during heat-shock or arsenite treatment, when poly-ubiquitinated proteins accumulate. Rpn13 ubiquitination strongly decreases the proteasome's ability to bind and degrade ubiquitin-conjugated proteins, but not its activity against peptide substrates. This autoinhibitory mechanism presumably evolved to prevent binding of ubiquitin conjugates to defective or stalled proteasomes, but this modification may also be useful as a biomarker indicating the presence of proteotoxic stress and reduced proteasomal capacity in cells or patients.


Subject(s)
Membrane Glycoproteins/metabolism , Proteasome Endopeptidase Complex/metabolism , Ubiquitination , Blotting, Western , Cell Line , Humans , Intracellular Signaling Peptides and Proteins , Membrane Glycoproteins/genetics , Proteasome Endopeptidase Complex/genetics
13.
Cell ; 150(4): 842-54, 2012 Aug 17.
Article in English | MEDLINE | ID: mdl-22901813

ABSTRACT

Due to genome instability, most cancers exhibit loss of regions containing tumor suppressor genes and collateral loss of other genes. To identify cancer-specific vulnerabilities that are the result of copy number losses, we performed integrated analyses of genome-wide copy number and RNAi profiles and identified 56 genes for which gene suppression specifically inhibited the proliferation of cells harboring partial copy number loss of that gene. These CYCLOPS (copy number alterations yielding cancer liabilities owing to partial loss) genes are enriched for spliceosome, proteasome, and ribosome components. One CYCLOPS gene, PSMC2, encodes an essential member of the 19S proteasome. Normal cells express excess PSMC2, which resides in a complex with PSMC1, PSMD2, and PSMD5 and acts as a reservoir protecting cells from PSMC2 suppression. Cells harboring partial PSMC2 copy number loss lack this complex and die after PSMC2 suppression. These observations define a distinct class of cancer-specific liabilities resulting from genome instability.


Subject(s)
Genes, Essential , Genomic Instability , Neoplasms/genetics , ATPases Associated with Diverse Cellular Activities , Animals , Cell Line, Tumor , Chromosome Deletion , Gene Dosage , Genes, Tumor Suppressor , Humans , Mice , Mice, Nude , Neoplasm Transplantation , Neoplasms/metabolism , Proteasome Endopeptidase Complex/genetics , Proteasome Endopeptidase Complex/metabolism , Transplantation, Heterologous
14.
Methods Mol Biol ; 832: 423-32, 2012.
Article in English | MEDLINE | ID: mdl-22350902

ABSTRACT

The standard methods for the isolation of the 26S proteasomes from mammalian tissues have long involved multiple chromatographic steps. This process led to loss of loosely associated regulatory proteins or cofactors and yielded particles with low functional capacity. Here, we describe a single-step affinity purification of 26S proteasome complexes that preserves the association with many 26S proteasome-interacting proteins. Our approach uses the ubiquitin-like domain of human RAD23B as an affinity bait, which allows the rapid and gentle isolation of 26S proteasomes with high purity. This strategy does not require the genetic introduction of tagged subunits nor expensive antibodies, and therefore can be used to isolate 26S proteasomes from any mammalian tissue or yeast. This method, therefore, is an important new tool to study 26S proteasome function in various models of human diseases that are linked to changes in the ubiquitin proteasome system, for example the increased proteasomal proteolysis seen in muscle wasting or the decreased proteasomal capacity that has been reported in various neurodegenerative diseases.


Subject(s)
Chromatography, Affinity/methods , DNA Repair Enzymes/metabolism , DNA-Binding Proteins/metabolism , Proteasome Endopeptidase Complex/analysis , Animals , Humans , Muscle, Skeletal/cytology , Proteasome Endopeptidase Complex/metabolism , Rats , Ubiquitins/metabolism
15.
J Biol Chem ; 285(51): 39597-608, 2010 Dec 17.
Article in English | MEDLINE | ID: mdl-20940294

ABSTRACT

Among the hallmarks of aged organisms are an accumulation of misfolded proteins and a reduction in skeletal muscle mass ("sarcopenia"). We have examined the effects of aging and dietary restriction (which retards many age-related changes) on components of the ubiquitin proteasome system (UPS) in muscle. The hindlimb muscles of aged (30 months old) rats showed a marked loss of muscle mass and contained 2-3-fold higher levels of 26S proteasomes than those of adult (4 months old) controls. 26S proteasomes purified from muscles of aged and adult rats showed a similar capacity to degrade peptides, proteins, and an ubiquitylated substrate, but differed in levels of proteasome-associated proteins (e.g. the ubiquitin ligase E6AP and deubiquitylating enzyme USP14). Also, the activities of many other deubiquitylating enzymes were greatly enhanced in the aged muscles. Nevertheless, their content of polyubiquitylated proteins was higher than in adult animals. The aged muscles contained higher levels of the ubiquitin ligase CHIP, involved in eliminating misfolded proteins, and MuRF1, which ubiquitylates myofibrillar proteins. These muscles differed from ones rapidly atrophying due to disease, fasting, or disuse in that Atrogin-1/MAFbx expression was low and not inducible by glucocorticoids. Thus, the muscles of aged rats showed many adaptations indicating enhanced proteolysis by the UPS, which may enhance their capacity to eliminate misfolded proteins and seems to contribute to the sarcopenia. Accordingly, dietary restriction decreased or prevented the aging-associated increases in proteasomes and other UPS components and reduced muscle wasting.


Subject(s)
Aging/metabolism , Muscle Proteins/metabolism , Muscle, Skeletal/metabolism , Proteasome Endopeptidase Complex/metabolism , Ubiquitin/metabolism , Ubiquitination/physiology , Animals , Male , Rats , Rats, Sprague-Dawley , SKP Cullin F-Box Protein Ligases/metabolism , Tripartite Motif Proteins , Ubiquitin-Protein Ligases/metabolism
16.
Article in English | MEDLINE | ID: mdl-20717473

ABSTRACT

Proteasome-mediated proteolysis is important for synaptic plasticity, neuronal development, protein quality control, and many other processes in neurons. To define proteasome composition in brain, we affinity purified 26S proteasomes from cytosolic and synaptic compartments of the rat cortex. Using tandem mass spectrometry, we identified the standard 26S subunits and a set of 28 proteasome-interacting proteins that associated substoichiometrically and may serve as regulators or cofactors. This set differed from those in other tissues and we also found several proteins that associated only with either the cytosolic or the synaptic proteasome. The latter included the ubiquitin-binding factor TAX1BP1 and synaptic vesicle protein SNAP-25. Native gel electrophoresis revealed a higher proportion of doubly-capped 26S proteasome (19S-20S-19S) in the cortex than in the liver or kidney. To investigate the interplay between proteasome regulation and synaptic plasticity, we exposed cultured neurons to glutamate receptor agonist NMDA. Within 4 h, this agent caused a prolonged decrease in the activity of the ubiquitin-proteasome system as shown by disassembly of 26S proteasomes, decrease in ubiquitin-protein conjugates, and dissociation of the ubiquitin ligases UBE3A (E6-AP) and HUWE1 from the proteasome. Surprisingly, the regulatory 19S particles were rapidly degraded by proteasomal, not lysosomal degradation, and the dissociated E3 enzymes also degraded. Thus the content of proteasomes and their set of associated proteins can be altered by neuronal activity, in a manner likely to influence synaptic plasticity and learning.

17.
Mol Cell ; 36(5): 794-804, 2009 Dec 11.
Article in English | MEDLINE | ID: mdl-20005843

ABSTRACT

In eukaryotic cells, ubiquitination of proteins leads to their degradation by the 26S proteasome. We tested if the ubiquitin (Ub) chain also regulates the proteasome's capacity for proteolysis. After incubation with polyubiquitinated proteins, 26S proteasomes hydrolyzed peptides and proteins 2- to 7-fold faster. Ub conjugates enhanced peptide hydrolysis by stimulating gate opening in the 20S proteasome. This stimulation was seen when this gate was closed or transiently open, but not maximally open. Gate opening requires conjugate association with Usp14/Ubp6 and also occurs if Ub aldehyde occupies this isopeptidase's active site. No stimulation was observed with 26S from Ubp6Delta mutants, but this effect was restored upon addition of Usp14/Ubp6 (even an inactive Ubp6). The stimulation of gate opening by Ub conjugates through Usp14/Ubp6 requires nucleotide binding to the gate-regulatory ATPases. This activation enhances the selectivity of the 26S proteasome for ubiquitinated proteins and links their deubiquitination to their degradation.


Subject(s)
Endopeptidases/metabolism , Proteasome Endopeptidase Complex/metabolism , Ubiquitin/metabolism , Adenosine Diphosphate/metabolism , Adenosine Triphosphatases/metabolism , Adenosine Triphosphate/analogs & derivatives , Adenosine Triphosphate/metabolism , Binding Sites , Hydrolysis , Models, Biological , Models, Molecular , Proteasome Endopeptidase Complex/chemistry , Ubiquitination
18.
Cell ; 138(1): 25-8, 2009 Jul 10.
Article in English | MEDLINE | ID: mdl-19596233

ABSTRACT

Assembly of complex structures such as the eukaryotic 26S proteasome requires intricate mechanisms that ensure precise subunit arrangements. Recent studies have shed light on the pathway for ordered assembly of the base of the 19S regulatory particle of the 26S proteasome by identifying new precursor complexes and four dedicated chaperones involved in its assembly.


Subject(s)
Proteasome Endopeptidase Complex/metabolism , Animals , Models, Biological , Molecular Chaperones/metabolism , Protein Subunits/metabolism
19.
Biochemistry ; 48(11): 2538-49, 2009 Mar 24.
Article in English | MEDLINE | ID: mdl-19182904

ABSTRACT

Recent studies, mainly in yeast, have identified various cofactors that associate with the 26S proteasome and appear to influence its function. To identify these proteins in different cells and physiological states, we developed a method to gently and rapidly isolate 26S proteasomes and associated proteins without the need for genetic modifications of the proteasome. This method is based on the affinity of this complex for the ubiquitin-like (UBL) domain of hHR23B and elution with a competing polypeptide containing a ubiquitin-interacting motif. Associated with 26S proteasomes from rat muscle were a variety of known proteasome-interacting proteins, activators, and ubiquitin conjugates. In addition, we identified over 40 proteins not previously known to associate with the 26S proteasome, some of which were tightly associated with the proteasome in a substoichiometric fashion, e.g., the deubiquitinating enzymes USP5/isopeptidase T and USP7/HAUSP and the ubiquitin ligases ARF-BP1/HUWE1 and p600/UBR4. By altering buffer conditions, we also purified by this approach complexes of the ATPase p97/VCP associated with its adaptor proteins Ufd1-Npl4, p47, SAKS1, and FAF1, all of which contain ubiquitin-binding motifs. These complexes were isolated with ubiquitin conjugates bound and were not previously known to bind to the UBL domain of hHR23B. These various UBL-interacting proteins, dubbed the UBL interactome, represent a network of proteins that function together in ubiquitin-dependent proteolysis, and the UBL method offers many advantages for studies of the diversity, functions, and regulation of 26S proteasomes and p97 complexes under different conditions.


Subject(s)
Adenosine Triphosphatases/metabolism , Cell Cycle Proteins/metabolism , DNA Repair Enzymes/metabolism , DNA-Binding Proteins/metabolism , Proteasome Endopeptidase Complex/metabolism , Adenosine Triphosphatases/genetics , Animals , Cell Cycle Proteins/genetics , DNA Repair Enzymes/chemistry , DNA Repair Enzymes/genetics , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , Humans , Muscle, Skeletal/metabolism , Proteasome Endopeptidase Complex/genetics , Protein Binding , Protein Structure, Tertiary , Rats , Valosin Containing Protein
20.
Eur J Biochem ; 271(22): 4361-5, 2004 Nov.
Article in English | MEDLINE | ID: mdl-15560777

ABSTRACT

A gene with significant similarity to bacterial Lon proteases was identified during the sequencing of the genome of the thermoacidophilic archaeon Thermoplasma acidophilum. Protein sequence comparison revealed that Thermoplasma Lon protease (TaLon) is more similar to the LonB proteases restricted to Gram-positive bacteria than to the widely distributed bacterial LonA. However, the active site residues of the protease and ATPase domain are highly conserved in all Lon proteases. Using site-directed mutagenesis we show here that TaLon and EcLon, and probably all other Lon proteases, contain a Ser-Lys dyad active site. The TaLon active site mutants were fully assembled and, similar to TaLon wild-type, displayed an apparent molar mass of 430 kDa upon gelfiltration. This would be consistent with a hexameric complex and indeed electron micrographs of TaLon revealed ring-shaped particles, although of unknown symmetry. Comparison of the ATPase activity of Lon wild-type from Thermoplasma or Escherichia coli with respective protease active site mutants revealed differences in Km and V values. This suggests that in the course of protein degradation by wild-type Lon the protease domain might influence the activity of the ATPase domain.


Subject(s)
Protease La/chemistry , Thermoplasma/enzymology , Amino Acid Sequence , Amino Acid Substitution , Archaeal Proteins/chemistry , Archaeal Proteins/genetics , Archaeal Proteins/metabolism , Binding Sites , Escherichia coli/enzymology , Fluorescein-5-isothiocyanate/chemistry , Fluorescein-5-isothiocyanate/metabolism , Kinetics , Lysine/chemistry , Lysine/metabolism , Molecular Sequence Data , Molecular Weight , Mutagenesis, Site-Directed , Protease La/genetics , Protease La/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Sequence Alignment , Serine/chemistry , Serine/metabolism
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