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Objective To identify key amino acid variations of major proteins from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by biophysical methods. Methods Through amino acid sequence alignment, classification of variant amino acid residues, three-dimensional structure reconstruction of proteins, and electrostatic interaction analysis of amino acid residues, the key amino acid variations of major proteins from SARS-CoV-2 was analyzed with RaTG13, the bat coronavirus with the highest homology, as the reference. Results At least ten amino acid variations that affect the possible electrostatic interactions were identified in RNA-dependent RNA polymerase (RdRp), exoribonuclease (ExoN), uridylate-specific endoribonuclease (NendoU), and spike (S) protein from SARS-CoV-2. These variations may affect the spatial conformation and biological functions of the proteins. Conclusion The key amino acid variations of the major proteins from SARS-CoV-2 have been preliminarily identified, providing clues for understanding the genetic, pathogenic and epidemiological characteristics of the virus..
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OBJECTIVE: To detect and analyze the degree of salivary acidification of rhEPO isoforms. METHODS: The isoelectric points of rhEPO isoforms were determined with full column imaging capillary isoelectric focusing electrophoresis. And the charge distribution among rhEPO isoforms was analyzed. The degrees of rhEPO's total saliva acidification were measured using the method of appendices of Chinese Pharmacopoeia. At last, the degrees of saliva acidification of rhEPO isoforms were obtained using multivariate linear fitting. RESULTS: Nine kinds of rhEPO isoforms were distinguished and defined as isoform 1 to 9 with isoelectric points in the range of 3.6 to 5.1. There was one sialic acid molecule between two contiguous rhEPO isoform. Furthermore, the degrees of salivary acidification of the main four kinds of isoforms, 4-7, were 13, 12, 11 and 10 mol/mol, respectively. CONCLUSION :This study lays foundation for rhEPO biosimilar evaluation and further analysis of each isoform of rhEPO.
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Objective To construct the recombinant RIP3 over-expressed plasmids and transfect them in breast cancer MCF7 cells, and identify the expression and localization of fusion protein, as well as its effect on the death way of MCF7 cells. Methods The expression levels of RIP3 mRNA in four breast cancer cell lines and normal mammary epithelial cells were detected by reverse transcription polymerase chain reaction (RT-PCR). The RIP 3 coding sequence was amplified by polymerase chain reaction and subcloned into mCherry vector to construct recombinant plasmids. The plasmids were transfected into MCF7 cells by lentivirus after DNA sequencing, then screened by basticidin (4 mg/L) for 1 week. The efficiencies of RIP3 expression were validated by Western blotting assay. The death way of mCherry-RIP3-MCF7 cells was observed under the treatment of TNF-αand Z-VAD-FMK. Results The lowest expression of RIP3 mRNA was found in MCF7 cells. The sequencing results validated the well recombinant plasmids. The expression of mCherry-RIP3 fusion pro-tein with a molecular weight of 85 ku was detected by Western blot assay. The mCherry-RIP3 expression enhanced the sensi-tivity of MCF7 cells to TNF-αand Z-VAD-FMK induced cell death. Conclusion The recombinant RIP3 over-expressed plasmids were successfully constructed, and the stable MCF7 cells with ectopic RIP3 transfection were obtained. The mCher-ry-RIP3 fusion protein was expressed in the cytoplasm and was conformed to mediate TNF-αinduced necroptosis.
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Homophilic interaction of the L1 family of cell adhesion molecules plays a pivotal role in regulating neurite outgrowth and neural cell networking in vivo. Functional defects in L1 family members are associated with neurological disorders such as X-linked mental retardation, multiple sclerosis, low-IQ syndrome, developmental delay, and schizophrenia. Various human tumors with poor prognosis also implicate the role of L1, a representative member of the L1 family of cell adhesion molecules, and ectopic expression of L1 in fibroblastic cells induces metastasis-associated gene expression. Previous studies on L1 homologs indicated that four N-terminal immunoglobulin-like domains form a horseshoe-like structure that mediates homophilic interactions. Various models including the zipper, domain-swap, and symmetry-related models are proposed to be involved in structural mechanism of homophilic interaction of the L1 family members. Recently, cryo-electron tomography of L1 and crystal structure studies of neurofascin, an L1 family protein, have been performed. This review focuses on recent discoveries of different models and describes the possible structural mechanisms of homophilic interactions of L1 family members. Understanding structural mechanisms of homophilic interactions in various cell adhesion proteins should aid the development of therapeutic strategies for L1 family cell adhesion molecule-associated diseases.
Subject(s)
Humans , Cell Adhesion , Crystallography, X-Ray , Escherichia coli , Immunoglobulins/chemistry , Neural Cell Adhesion Molecule L1/chemistry , Neurites/chemistry , Protein Conformation , Protein Interaction Domains and MotifsABSTRACT
Objective To study the protein conformational change of placenta tissue by using Raman spectrum.Methods By using Raman spectroanalysis,we detected the placenta protein conformational change of GDM and control groups.Results(1)In the placenta of GDM,the absorption bands of tryptophan and phenylalanine were increased obviously.(2)In the placenta of GDM,the secondary structure of protein was composed of α-helix,random coil and β-sheet.Conclusions In the placenta of GDM,the orderly conformations of main chains in protein are decreased.Side chains of amino acids,especially tryptophan and phenyl-alanine,are changed greatly.The structure variation of protein may be correlated to the diabetic complications.
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Whether protein could adopt multiple conformations coexisting in solution is disputable. In a previous report,the conformation heterogeneity of apoazurin mutant M121L had been identified. The thermal unfolding of wild type apoazurin from Pseudomonas aeruginosa is re-investigated with differential scanning calorimetry (DSC) and circular dichroism (CD) methods. The results show that unfolding in the pH range from 4 to 9 is associated with two heat capacity maxima. The low temperature transitions are reversible at all pH conditions used, while the high temperature transitions are irreversible. The two unfolding transitions were analyzed by the two-interchangeable-conformation model with the fraction for the first transition (N1) from 64% at pH 4.0 to 55% at pH 9.0. Temperature induced unfolding monitored at 219 nm shows also two separate transitions. The ratio of the signal changes is consistent with the fractions obtained from the corresponding DSC measurements. These results provide further support for the hypothesis that at least two conformations of apoazurin coexists in solution.
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BACKGROUND: There has been a lack of study on the structural changes of serum albumin in patients with minimal change disease (MCD). To determine whether glycation and/or conformational transitions of albumin are involved in the pathogenesis of albuminuria, nine patients with MCD were enrolled in a prospective follow-up study for comparison of these parameters in serum albumin during the remission and relapse of nephrotic syndrome. METHODS: Circular dichroism measurements were made with purified albumin. Ellipticities at each wavelength were transformed to mean residue ellipticity. Monosaccharide composition was analyzed by high-pH anion-exchange chromatography with pulsed amperometric detection. RESULTS: There was no difference in the proportions of alpha-helix, beta-conformation, and beta-turn of albumin between the sera of control patients and those with nephrotic syndrome. However, the proportion of the random configuration was slightly higher in the plasma albumin of patients in relapse than in those in remission. The proportion of the random configuration was lower in the albumin of the serum than in the urine of patients with nephrotic syndrome, but there was no difference in the proportions of alpha-helix, beta-conformation, and beta-turn of albumin between their plasma and urine. CONCLUSION: Our results suggest that conformational changes in albumin are involved in albuminuria in patients with MCD.