Lifestyle can be anything if not defined. A review of understanding and use of the lifestyle concept in sustainability studies.

A holistic understanding of human behaviour is considered key for a successful fight against climate change and environmental degradation. In the pursuit of a holistic understanding, empirical research frequently applies the concept of "lifestyle". The concept, which plays a significant role in segmenting customers in the field of marketing, is increasingly used in the cross-domain analysis of behaviour in the field of sustainability. This increase is tied to the challenge that the meaning and operationalisation of the lifestyle concept are still highly fragmented after decades of empirical studies. While this methodological heterogeneity and pluralism of research traditions bring creativity and dynamic to the field, it makes the orientation and a comparison of studies challenging. Previous attempts to streamline lifestyle oriented research have often aimed for a single mode of operationalisation, but this does not meet the diversity of possible applications of the concept. Therefore, a better understanding of the field seems necessary. To fill this gap, we review the understanding and use of the "lifestyle" concept in 53 empirical studies in the field of sustainability and identify 12 variants of lifestyle related research, differing along three dimensions. According to our results, (I) lifestyle can either be used as a cause or as a consequence, (II) the analytical scope can be on a micro-, meso- or macro level, and (III) the behavioural scope can be either limited to a single behavioural domain or cover multiple domains. The three dimensions allow a mapping of existing and future empirical research using the "lifestyle" concept, improve the orientation in the field, facilitate the identification of relevant studies, and avoid imprecise comparisons due to methodological differences.

Feeling hot is being hot? Comparing the mapping and the surveying paradigm for urban heat vulnerability in Vienna.

With rising global temperatures, cities increasingly need to identify populations or areas that are vulnerable to urban heat waves; however, vulnerability assessments may run into ecological fallacy if data from different scales are misconstrued as equivalent. We assess the heat vulnerability of 1983 residents in Vienna by measuring heat impacts, exposure, sensitivity and adaptive capacity with mirrored indicators in the mapping paradigm (i.e. census tract data referring to the geographic regions where these residents live) and the surveying paradigm (i.e. survey data referring to the residents' individual households). Results obtained in both paradigms diverge substantially: meteorological indicators of hot days and tropical nights are virtually unrelated to self-reported heat strain. Meteorological indicators are explained by mapping indicators (R2 of 15-40 %), but mostly not by surveying indicators. Vice versa, experienced heat stress and subjective heat burden are mostly unassociated with mapping indicators but are partially explained by surveying indicators (R2 of 2-4 %). The results suggest that the two paradigms do not capture the same components of vulnerability; this challenges whether studies conducted in the respective paradigms can complement and cross-validate each other. Policy interventions should first define which heat vulnerability outcome they target and then apply the paradigm that best captures the specific drivers of this outcome.

NMR-Based Metabolite Profiling and the Application of STOCSY toward the Quality and Authentication Assessment of European EVOOs.

Extra virgin olive oil (EVOO) possesses a high-value rank in the food industry, thus making it a common target for adulteration. Hence, several methods have been essentially made available over the years. However, the issue of authentication remains unresolved with national and food safety organizations globally struggling to regulate and control its market. Over the course of this study, the aim was to determine the origin of EVOOs suggesting a high-throughput, state-of-the-art method that could be easily adopted. A rapid, NMR-based untargeted metabolite profiling method was applied and complemented by multivariate analysis (MVA) and statistical total correlation spectroscopy (STOCSY). STOCSY is a valuable statistical tool contributing to the biomarker identification process and was employed for the first time in EVOO analysis. Market samples from three Mediterranean countries of Spain, Italy, and Greece, blended samples from these countries, as well as monocultivar samples from Greece were analyzed. The NMR spectra were collected, with the help of chemometrics acting as "fingerprints" leading to the discovery of certain chemical classes and single biomarkers that were related to the classification of the samples into groups based on their origin.

The Impact of Exercise on Telomere Length, DNA Methylation and Metabolic Footprints.

Aging as a major risk factor influences the probability of developing cancer, cardiovascular disease and diabetes, amongst others. The underlying mechanisms of disease are still not fully understood, but research suggests that delaying the aging process could ameliorate these pathologies. A key biological process in aging is cellular senescence which is associated with several stressors such as telomere shortening or enhanced DNA methylation. Telomere length as well as DNA methylation levels can be used as biological age predictors which are able to detect excessive acceleration or deceleration of aging. Analytical methods examining aging are often not suitable, expensive, time-consuming or require a high level of technical expertise. Therefore, research focusses on combining analytical methods which have the potential to simultaneously analyse epigenetic, genomic as well as metabolic changes.

Impact of Global Climate Change on the European Barley Market Requires Novel Multi-Method Approaches to Preserve Crop Quality and Authenticity.

Most recently in 2018 and 2019, large parts of Europe were affected by periods of massive drought. Resulting losses in cereal yield pose a major risk to the global supply of barley, as more than 60% of global production is based in Europe. Despite the arising price fluctuations on the cereal market, authenticity of the crop must be ensured, which includes correct declaration of harvest years. Here, we show a novel approach that allows such differentiation for spring barley samples, which takes advantage of the chemical changes caused by the extreme drought. Samples from 2018 were successfully differentiated from those of 2017 by analysis of changes in near-infrared spectra, enrichment in the isotope 13C, and strong accumulation of the plant-physiological marker betaine. We demonstrate that through consideration of multiple modern analysis techniques, not only can fraudulent labelling be prevented, but indispensable knowledge on the drought tolerance of crops can be obtained.

Towards standardized purification of bacterial magnetic nanoparticles for future in vivo applications.

Bacterial magnetosomes (MS) are well-defined membrane-enveloped single-domain iron oxide (magnetite) nanoparticles, which are susceptible to genetic and chemical engineering. Additionally, the possibility to manipulate these particles by external magnetic fields facilitates their application in biomedicine and biotechnology, e.g. as magnetic resonance imaging probes or for drug delivery purposes. However, current purification protocols are poorly characterized, thereby hampering standardized and reproducible magnetosome production and thus, reliable testing for in vivo applications. In that context, the establishment of reproducible particle isolation procedures as well as the identification of high quality control parameters and the evaluation of potential cytotoxic effects of purified particles are of major importance. In this study, we characterize a multi-step purification protocol for MS with regard to purity, iron content, size and polydispersity of magnetite particles. In addition, we address potential cytotoxic effects of isolated MS when incubated with mammalian cells. Overall, we provide a detailed overview of the process-structure relationship during the isolation of MS and thus, identify prerequisites for high-yield MS production and their future application in the biomedical and biotechnological field. STATEMENT OF SIGNIFICANCE: Magnetic nanoparticles are of increasing interest for a variety of biomedical and biotechnological applications. Due to their unprecedented material characteristics, bacterial magnetosomes represent a promising alternative to chemically synthesized iron oxide nanoparticles. As applications require well-defined, highly purified and fully characterized nanoparticles, reliable protocols are necessary for efficient and reproducible magnetosome isolation. In our study, we evaluate an improved magnetosome extraction procedure and monitor quality parameters such as particle size distribution, membrane integrity and purity of the suspension by a combination of physicochemical and biochemical methods. Furthermore, the cytotoxicity of the isolated magnetosomes is assessed using different cell lines. In summary, our study helps to establish prerequisites for many real-world applications of magnetosomes in the field of biotechnology and biomedicine.

Guava (Psidium guajava) Fruit Extract Prepared by Supercritical CO2 Extraction Inhibits Intestinal Glucose Resorption in a Double-Blind, Randomized Clinical Study.

Inhibition of intestinal glucose resorption can serve as an effective strategy for the prevention of an increase in blood glucose levels. We have recently shown that various extracts prepared from guava (Psidium guajava) inhibit sodium-dependent glucose cotransporter 1 (SGLT1)- and glucose transporter 2 (GLUT2)-mediated glucose transport in vitro (Caco-2 cells) and in vivo (C57BL/6N mice). However, the efficacy in humans remains to be confirmed. For this purpose, we conducted a parallelized, randomized clinical study with young healthy adults. Thirty-one volunteers performed an oral glucose tolerance test (OGTT) in which the control group received a glucose solution and the intervention group received a glucose solution containing a guava fruit extract prepared by supercritical CO2 extraction. The exact same extract was used for our previous in vitro and in vivo experiments. Blood samples were collected prior to and up to two hours after glucose consumption to quantitate blood glucose and insulin levels. Our results show that, in comparison to the control group, consumption of guava fruit extract resulted in a significantly reduced increase in postprandial glucose response over the basal fasting plasma glucose levels after 30 min (Δ control 2.60 ± 1.09 mmol/L versus Δ intervention 1.96 ± 0.96 mmol/L; p = 0.039) and 90 min (Δ control 0.44 ± 0.74 mmol/L versus Δ intervention -0.18 ± 0.88 mmol/L; p = 0.023). In addition, we observed a slightly reduced, but non-significant insulin secretion (Δ control 353.82 ± 183.31 pmol/L versus Δ intervention 288.43 ± 126.19 pmol/L, p = 0.302). Interestingly, storage time and repeated freeze-thawing operations appeared to negatively influence the efficacy of the applied extract. Several analytical methods (HPLC-MS, GC-MS, and NMR) were applied to identify putative bioactive compounds in the CO2 extract used. We could assign several substances at relevant concentrations including kojic acid (0.33 mg/mL) and 5-hydroxymethylfurfural (2.76 mg/mL). Taken together, this clinical trial and previous in vitro and in vivo experiments confirm the efficacy of our guava fruit extract in inhibiting intestinal glucose resorption, possibly in combination with reduced insulin secretion. Based on these findings, the development of food supplements or functional foods containing this extract appears promising for patients with diabetes and for the prevention of insulin resistance. Trial registration: 415-E/2319/15-2018 (Ethics Commissions of Salzburg).

Complementary use of 1H NMR and multi-element IRMS in association with chemometrics enables effective origin analysis of cocoa beans (Theobroma cacao L.).

Within the cocoa market (Theobroma cacao L.), quality and prices are often determined by geographical origin, making traceability indispensable. Therefore, to investigate possibilities of tracing by analytical methods, 48 carefully selected cocoa samples from 20 countries have been profiled using a combination of stable isotope-ratio mass spectrometry (IRMS) and proton nuclear magnetic resonance (1H NMR). Chemometric analysis of combined data sets from both, stable isotope data (δ13C, δ15N, δ18O, δ2H, %C, %N, %O, %H) and 1H NMR fingerprints, achieved good separation with increased classification rates compared to classification with data of the isolated methods. IRMS contributed primarily to discrimination between countries, while 1H NMR significantly contributed to separation of varieties, but also the regions within individual countries. This study thus demonstrates that combination of two analytical methods is an effective tool to enhance both, accuracy and precision, in authenticity testing of cocoa.

Acidic Residues Control the Dimerization of the N-terminal Domain of Black Widow Spiders' Major Ampullate Spidroin 1.

Dragline silk is the most prominent amongst spider silks and comprises two types of major ampullate spidroins (MaSp) differing in their proline content. In the natural spinning process, the conversion of soluble MaSp into a tough fiber is, amongst other factors, triggered by dimerization and conformational switching of their helical amino-terminal domains (NRN). Both processes are induced by protonation of acidic residues upon acidification along the spinning duct. Here, the structure and monomer-dimer-equilibrium of the domain NRN1 of Latrodectus hesperus MaSp1 and variants thereof have been investigated, and the key residues for both could be identified. Changes in ionic composition and strength within the spinning duct enable electrostatic interactions between the acidic and basic pole of two monomers which prearrange into an antiparallel dimer. Upon naturally occurring acidification this dimer is stabilized by protonation of residue E114. A conformational change is independently triggered by protonation of clustered acidic residues (D39, E76, E81). Such step-by-step mechanism allows a controlled spidroin assembly in a pH- and salt sensitive manner, preventing premature aggregation of spider silk proteins in the gland and at the same time ensuring fast and efficient dimer formation and stabilization on demand in the spinning duct.

Structural transitions in full-length human prion protein detected by xenon as probe and spin labeling of the N-terminal domain.

Fatal neurodegenerative disorders termed transmissible spongiform encephalopathies (TSEs) are associated with the accumulation of fibrils of misfolded prion protein PrP. The noble gas xenon accommodates into four transiently enlarged hydrophobic cavities located in the well-folded core of human PrP(23-230) as detected by [(1)H, (15)N]-HSQC spectroscopy. In thermal equilibrium a fifth xenon binding site is formed transiently by amino acids A120 to L125 of the presumably disordered N-terminal domain and by amino acids K185 to T193 of the well-folded domain. Xenon bound PrP was modelled by restraint molecular dynamics. The individual microscopic and macroscopic dissociation constants could be derived by fitting the data to a model including a dynamic opening and closing of the cavities. As observed earlier by high pressure NMR spectroscopy xenon binding influences also other amino acids all over the N-terminal domain including residues of the AGAAAAGA motif indicating a structural coupling between the N-terminal domain and the core domain. This is in agreement with spin labelling experiments at positions 93 or 107 that show a transient interaction between the N-terminus and the start of helix 2 and the end of helix 3 of the core domain similar to that observed earlier by Zn(2+)-binding to the octarepeat motif.

Resonance assignment of an engineered amino-terminal domain of a major ampullate spider silk with neutralized charge cluster.

Spider dragline fibers are predominantly made out of the major ampullate spidroins (MaSp) 1 and 2. The assembly of dissolved spidroin into a stable fiber is highly controlled for example by dimerization of its amino-terminal domain (NRN) upon acidification, as well as removal of sodium chloride along the spinning duct. Clustered residues D39, E76 and E81 are the most highly conserved residues of the five-helix bundle, and they are hypothesized to be key residues for switching between a monomeric and a dimeric conformation. Simultaneous replacement of these residues by their non-titratable analogues results in variant D39N/E76Q/E81Q, which is supposed to fold into an intermediate conformation between that of the monomeric and the dimeric state at neutral pH. Here we report the resonance assignment of Latrodectus hesperus NRN variant D39N/E76Q/E81Q at pH 7.2 obtained by high-resolution triple resonance NMR spectroscopy.

Disturbed neuronal ER-Golgi sorting of unassembled glycine receptors suggests altered subcellular processing is a cause of human hyperekplexia.

Recent studies on the pathogenic mechanisms of recessive hyperekplexia indicate disturbances in glycine receptor (GlyR) α1 biogenesis. Here, we examine the properties of a range of novel glycine receptor mutants identified in human hyperekplexia patients using expression in transfected cell lines and primary neurons. All of the novel mutants localized in the large extracellular domain of the GlyR α1 have reduced cell surface expression with a high proportion of receptors being retained in the ER, although there is forward trafficking of glycosylated subpopulations into the ER-Golgi intermediate compartment and cis-Golgi compartment. CD spectroscopy revealed that the mutant receptors have proportions of secondary structural elements similar to wild-type receptors. Two mutants in loop B (G160R, T162M) were functional, but none of those in loop D/ß2-3 were. One nonfunctional truncated mutant (R316X) could be rescued by coexpression with the lacking C-terminal domain. We conclude that a proportion of GlyR α1 mutants can be transported to the plasma membrane but do not necessarily form functional ion channels. We suggest that loop D/ß2-3 is an important determinant for GlyR trafficking and functionality, whereas alterations to loop B alter agonist potencies, indicating that residues here are critical elements in ligand binding.

Prosequence switching: an effective strategy to produce biologically active E. coli heat-stable enterotoxin STh.

Enterotoxigenic Escherichia coli (ETEC) infections account for the majority of cases of acute secretory diarrhea. The causative agents are enterotoxins secreted by ETEC, among them is the heat-stable enterotoxin, STh. STh is a 19-amino acid peptide containing three disulfide bonds that stimulates fluid secretion in the bowel by binding to the receptor domain of intestinal guanylyl cyclase C (GC-C). Since GC-C agonists have pharmacologic potential for diagnosis and treatment of disorders such as constipation-predominant irritable bowel syndrome (IBS-C), chronic constipation, and colorectal carcinoma, it is crucial to develop methods for the large-scale production of STh and related peptides. Here, we present a strategy for recombinant expression of STh that relies on the use of the prosequence of human uroguanylin to support proper folding and disulfide bond formation. The chimeric protein CysCys-STh consisting of the propeptide of uroguanylin as N-terminus and the STh peptide as C-terminus was expressed in E. coli, and an efficient purification protocol was developed. Trypsin digestion of this protein released the enterotoxin which could be obtained in high purity. NMR and mass spectrometry confirmed the identity and homogeneity of the toxin, and its biological activity was confirmed by a cell-based in vivo assay. The expression scheme introduced here represents a cost-efficient and scalable way of STh production.

The CoxD protein, a novel AAA+ ATPase involved in metal cluster assembly: hydrolysis of nucleotide-triphosphates and oligomerization.

CoxD of the α-proteobacterium Oligotropha carboxidovorans is a membrane protein which is involved in the posttranslational biosynthesis of the [CuSMoO2] cluster in the active site of the enzyme CO dehydrogenase. The bacteria synthesize CoxD only in the presence of CO. Recombinant CoxD produced in E. coli K38 pGP1-2/pETMW2 appeared in inclusion bodies from where it was solubilized by urea and refolded by stepwise dilution. Circular dichroism spectroscopy revealed the presence of secondary structural elements in refolded CoxD. CoxD is a P-loop ATPase of the AAA-protein family. Refolded CoxD catalyzed the hydrolysis of MgATP yielding MgADP and inorganic phosphate at a 1∶1∶1 molar ratio. The reaction was inhibited by the slow hydrolysable MgATP-γ-S. GTPase activity of CoxD did not exceed 2% of the ATPase activity. Employing different methods (non linear regression, Hanes and Woolf, Lineweaver-Burk), preparations of CoxD revealed a mean K(M) value of 0.69±0.14 mM ATP and an apparent V(max) value of 19.3±2.3 nmol ATP hydrolyzed min⁻¹ mg⁻¹. Sucrose density gradient centrifugation and gel filtration showed that refolded CoxD can exist in various multimeric states (2-mer, 4-mer or 6-mer), preferentially as hexamer or dimer. Within weeks the hexamer dissociates into the dimer, a process which can be reversed by MgATP or MgATP-γ-S within hours. Only the hexamers and the dimers exhibited MgATPase activity. Transmission electron microscopy of negatively stained CoxD preparations revealed distinct particles within a size range of 10-16 nm, which further corroborates the oligomeric organization. The 3D structure of CoxD was modeled with the 3D structure of BchI from Rhodobacter capsulatus as template. It has the key elements of an AAA+ domain in the same arrangement and at same positions as in BchI and displays the characteristic inserts of the PS-II-insert clade. Possible functions of CoxD in [CuSMoO2] cluster assembly are discussed.

An inhibitory peptide derived from the α-subunit of the epithelial sodium channel (ENaC) shows a helical conformation.

Proteolytic activation of the heteromeric epithelial sodium channel (ENaC) is thought to involve the release of inhibitory peptides from the extracellular domains of its α- and γ-subunit. Recently, we demonstrated that an α-13-mer peptide, corresponding to a putative inhibitory region within the extracellular domain of human αENaC, inhibits human αßγENaC. The aim of the present study was to investigate the structural basis of the inhibitory effect of this α-13-mer peptide. Analysis of the peptide by replica exchange molecular dynamics method, circular dichroism spectroscopy, nuclear magnetic resonance spectroscopy, and molecular dynamics simulations suggested that a helical turn at the carboxy-terminus is the preferred conformational state of the α-13-mer peptide. From this we predicted that a specific mutation (leucine 188 to alanine) should have a strong effect on the conformational preferences of the peptide. To functionally test this, we compared the effect of the wild-type α-13-mer with that of a mutant α-L188A-13-mer on ENaC currents in Xenopus laevis oocytes heterologously expressing human αßγENaC. We demonstrated that replacing the leucine 188 by alanine abolished the inhibitory effect of the α-13-mer peptide on ENaC. These findings suggest that a helical conformation in its carboxyterminal part is functionally important to mediate ENaC inhibition by the α-13-mer peptide. However, high resolution structural information on the complex of the inhibitory αENaC peptide and the channel are needed to confirm this conclusion.

The Fe(II)/α-ketoglutarate-dependent taurine dioxygenases from Pseudomonas putida and Escherichia coli are tetramers.

Fe(II)/α-ketoglutarate-dependent oxygenases are versatile catalysts associated with a number of different biological functions in which they use the oxidizing power of activated dioxygen to convert a variety of substrates. A mononuclear nonheme iron center is used to couple the decarboxylation of the cosubstrate α-ketoglutarate with a two-electron oxidation of the substrate, which is a hydroxylation in most cases. Although Fe(II)/α-ketoglutarate-dependent oxygenases have diverse amino acid sequences and substrate specifity, it is assumed that they share a common mechanism. One representative of this enzyme family is the Fe(II)/α-ketoglutarate-dependent taurine dioxygenase that catalyzes the hydroxylation of taurine yielding sulfite and aminoacetaldehyde. Its mechanism has been studied in detail becoming a model system for the whole enzyme family. However, its oligomeric state and architecture have been disputed. Here, we report the biochemical and kinetic characterization of the Fe(II)/α-ketoglutarate-dependent taurine dioxygenase from Pseudomonas putida KT2440 (TauD(Pp) ). We also present three crystal structures of the apo form of this enzyme. Comparisons with taurine dioxygenase from Escherichia coli (TauD(Ec) ) demonstrate that both enzymes are quite similar regarding their spectra, structure and kinetics, and only minor differences for the accumulation of intermediates during the reaction have been observed. Structural data and analytical gel filtration, as well as sedimentation velocity analytical ultracentrifugation, show that both TauD(Pp) and TauD(Ec) are tetramers in solution and in the crystals, which is in contrast to the earlier description of taurine dioxygenase from E. coli as a dimer. Database The atomic coordinates and structure factors have been deposited with the Brookhaven Protein Data Bank (entry 3PVJ, 3V15, 3V17) Structured digital abstract • tauDpp and tauDpp bind by molecular sieving (View interaction) • tauDpp and tauDpp bind by x-ray crystallography (View interaction) • tauDEc and tauDEc bind by molecular sieving (View interaction).

Energy landscape of the prion protein helix 1 probed by metadynamics and NMR.

The characterization of the structural dynamics of proteins, including those that present a substantial degree of disorder, is currently a major scientific challenge. These dynamics are biologically relevant and govern the majority of functional and pathological processes. We exploited a combination of enhanced molecular simulations of metadynamics and NMR measurements to study heterogeneous states of proteins and peptides. In this way, we determined the structural ensemble and free-energy landscape of the highly dynamic helix 1 of the prion protein (PrP-H1), whose misfolding and aggregation are intimately connected to a group of neurodegenerative disorders known as transmissible spongiform encephalopathies. Our combined approach allowed us to dissect the factors that govern the conformational states of PrP-H1 in solution, and the implications of these factors for prion protein misfolding and aggregation. The results underline the importance of adopting novel integrated approaches that take advantage of experiments and theory to achieve a comprehensive characterization of the structure and dynamics of biological macromolecules.

Fast mapping of biomolecular interfaces by Random Spin Labeling (RSL).

Random spin labeling (RSL) is a method for rapid mapping of biomolecular interaction surfaces using an interaction partner with SL and an interaction partner enriched in (13)C or (15)N nuclei for paramagnetic relaxation enhanced NMR-based detection. The SL reaction is conducted in a manner resulting in a heterogeneous reaction product consisting of different populations of the protein carrying a varying number of spin labels at different positions. Preparation of the paramagnetic probe is complete within a few hours and hence much faster than site selective SL. RSL is applicable to tightly interacting systems but shows its particular strength when applied to systems involving weak or transient contacts.

The therapeutically anti-prion active antibody-fragment scFv-W226: paramagnetic relaxation-enhanced NMR spectroscopy aided structure elucidation of the paratope-epitope interface.

Antibodies have become indispensable reagents with numerous applications in biological and biotechnical analysis, in diagnostics as well as in therapy. In all cases, selective interaction with an epitope is crucial and depends on the conformation of the paratope. While epitopes are routinely mapped at high throughput, methods revealing structural insights on a rather short timescale are rare. We here demonstrate paramagnetic relaxation-enhanced (PRE) NMR spectroscopy to be a powerful tool unraveling structural information about epitope-orientation in a groove spanned by the complementary determining regions. In particular, we utilize the spin label TOAC, which is fused to the peptidic epitope using standard solid-phase chemistry and which is characterized by a reduced mobility compared to, e.g., spin labels attached to the side-chain functionalities of cysteine or lysine residues. We apply the method to determine the orientation of helix 1 of the prion protein, which is the epitope for the therapeutically anti-prion active scF(v) fragment W226.

Formation of transient dimers by a retroviral protease.

Retroviral proteases have been shown previously to be only active as homodimers. They are essential to form the separate and active proteins from the viral precursors. Spumaretroviruses produce separate precursors for Gag and Pol, rather than a Gag and a Gag-Pol precursor. Nevertheless, processing of Pol into a PR (protease)-RT (reverse transcriptase) and integrase is essential in order to obtain infectious viral particles. We showed recently that the PR-RT from a simian foamy virus, as well as the separate PRshort (protease) domain, exhibit proteolytic activities, although only monomeric forms could be detected. In the present study, we demonstrate that PRshort and PR-RT can be inhibited by the putative dimerization inhibitor cholic acid. Various other inhibitors, including darunavir and tipranavir, known to prevent HIV-1 PR dimerization in cells, had no effect on foamy virus protease in vitro. 1H-15N HSQC (heteronuclear single quantum coherence) NMR analysis of PRshort indicates that cholic acid binds in the proposed PRshort dimerization interface and appears to impair formation of the correct dimer. NMR analysis by paramagnetic relaxation enhancement resulted in elevated transverse relaxation rates of those amino acids predicted to participate in dimer formation. Our results suggest transient PRshort homodimers are formed under native conditions but are only present as a minor transient species, which is not detectable by traditional methods.