In Gram-positive bacteria, sortase enzymes assemble surface proteins and pili in the cell wall envelope. Sortases catalyze a transpeptidation reaction that joins a highly conserved LPXTG sorting signal within their polypeptide substrate to the cell wall or to other pilin subunits. The molecular basis of transpeptidation and sorting signal recognition are not well understood, because the intermediates of catalysis are short lived. We have overcome this problem by synthesizing an analog of the LPXTG signal whose stable covalent complex with the enzyme mimics a key thioacyl catalytic intermediate. Here we report the solution structure and dynamics of its covalent complex with the Staphylococcus aureus SrtA sortase. In marked contrast to a previously reported crystal structure, we show that SrtA adaptively recognizes the LPXTG sorting signal by closing and immobilizing an active site loop. We have also used chemical shift mapping experiments to localize the binding site for the triglycine portion of lipid II, the second substrate to which surface proteins are attached. We propose a unified model of the transpeptidation reaction that explains the functions of key active site residues. Since the sortase-catalyzed anchoring reaction is required for the virulence of a number of bacterial pathogens, the results presented here may facilitate the development of new anti-infective agents.Bacterial surface proteins function as virulence factors that enable pathogens to adhere to sites of infection, evade the immune response, acquire essential nutrients, and enter host cells (1). Gram-positive bacteria use a common mechanism to covalently attach proteins to the cell wall. This process is catalyzed by sortase transpeptidase enzymes, which join proteins bearing a highly conserved Leu-Pro-X-Thr-Gly (LPXTG, where X is any amino acid) sorting signal to the cross-bridge peptide of the peptidylglycan (2-4). Sortases also polymerize proteins containing sorting signals into pili, filamentous surface exposed structures that promote bacterial adhesion (5, 6). The search for small molecule sortase inhibitors is an active area of research, since these enzymes contribute to the virulence of a number of important pathogens, including among others Staphylococcus aureus, Listeria monocytogenes, Streptococcus pyogenes, and Streptococcus pneumoniae (reviewed in Refs. 7 and 8). Sortase enzymes are also promising molecular biology reagents that can be used to site-specifically attach proteins to a variety of biomolecules (9 -14, 72).The sortase A (SrtA) 7 enzyme from S. aureus is the prototypical member of the sortase enzyme family (15, 16). It anchors proteins to the murein sacculus that possess a COOH-terminal cell wall sorting signal that consists of a LPXTG motif, followed by a hydrophobic segment of amino acids and a tail composed of mostly positively charged residues (17). SrtA is located on the extracellular side of the membrane. After partial secretion of its protein substrate across the cell membrane, SrtA cleaves the LPXTG motif between...

Many virulence factors in GramSurface proteins on bacteria are frequently virulence factors, promoting bacterial adhesion, resistance to phagocytic killing, and host cell invasion during infection. In Gram-positive bacteria these proteins are often covalently anchored to the cell wall by sortase enzymes, a family of novel cysteine transpeptidases (1-3). The sortase A protein (SrtA) 2 from Staphylococcus aureus has been characterized extensively (4) and anchors proteins bearing a cell wall sorting signal that consists of a conserved LPXTG motif (where X is any amino acid), a hydrophobic domain, and a tail of mostly positively charged residues (4 -6). SrtA cleaves in between the threonine and glycine of the LPXTG motif (7) and catalyzes the formation of a peptide bond between the carboxylgroup of the threonine and the amine-group of the cell-wall precursor lipid II (7-9). The lipid II-linked protein is then incorporated into the peptidoglycan of the cell wall via the transglycosylation and transpeptidation reactions of bacterial cell-wall synthesis. Sortases represent an attractive target for new anti-infective agents, because they are widely distributed among a variety of bacterial pathogens (10, 11) (e.g. Bacillus anthracis, Listeria monocytogenes, Streptococcus pneumoniae, and Streptococcus pyogenes), and have been shown to be required for virulence (12-16).The catalytic domain of SrtA (SrtA ⌬N59 , residues 60 -206) adopts a conserved eight-stranded ␤-barrel fold (17, 18). The active site is organized around the catalytically essential side chain of Cys-184, whose thiolate nucleophilically attacks the threonine carbonyl carbon within the LPXTG sorting signal, forming a thioester linkage between the enzyme and substrate (19). In addition to Cys-184, the hydrophilic side chains of His-120 and Arg-197 are absolutely required for catalysis (20 -22). These residues likely participate in general acid/base catalysis, and one of them must activate the thiol for nucleophilic attack, because it is protonated at neutral pH (23). The indole ring of Trp-194 partially shields the cysteine thiol from the solvent, and its mutation to alanine reduces enzyme activity 4-fold through an unknown mechanism (20). Using NMR and crystallography, the LPXTG sorting signal binding site has recently been localized to a surface formed by strands ␤4 and ␤7, and to a proximal loop that connects strands ␤6 to ␤7(the ␤6/␤7 loop) (18,22). Substrate binding may occur through an induced-fit mechanism involving conformational changes in the ␤6/␤7 loop, because it is disordered in the absence of the sorting signal substrate (17,18). Ca 2ϩ stimulates the activity of SrtA ⌬N59 in vitro (17) and may enable S. aureus to increase the rate of surface protein anchoring as it encounters elevated concentrations of this ion at sites of infection. Because many surface proteins function as virulence factors, the stimulatory effect of Ca 2ϩ likely plays an important role in the infection process. Previously we showed that Ca 2ϩ bound to an ordered pocket positio...

Methicillin resistant Staphylococcus aureus (MRSA) is a major health problem that has created a pressing need for new antibiotics. Compounds that inhibit the S. aureus SrtA sortase may function as potent anti-infective agents as this enzyme attaches virulence factors to the cell wall. Using highthroughput screening, we have identified several compounds that inhibit the enzymatic activity of the SrtA. A structure-activity relationship (SAR) analysis led to the identification of several pyridazinone and pyrazolethione analogs that inhibit SrtA with IC 50 values in the sub-micromolar range. Many of these molecules also inhibit the sortase enzyme from Bacillus anthracis suggesting that they may be generalized sortase inhibitors.

Introduction Castration resistant prostate cancer (CRPC) has a historically low median survival rate but recent advances and discoveries in micro RNAs (miRNAs) have opened the potential for new prognostication modalities to enhance therapeutic success. As new chemotherapies and immunotherapies are developed there is an increasing need for precision and stratification of CRPC to allow for optimization and personalization of therapy. Methods A systematic literature review was conducted via electronic database resulting in the selection of forty-two articles based on title, abstract, study format, and content by a consensus of all participating authors. The majority of selected articles were published between 2002 and 2013. In this review, we will discuss the robustness of miRNAs as a biomarker platform, miRNAs associated with prostate cancer, and recent discoveries of miRNA associations with CRPC. Results The associations discovered have been of interest due to the ability to differentiate between CRPC and localized prostate cancer. With evaluation of multiple miRNAs, it is possible to provide a profile in regards to tumor characteristics. Furthermore, actions of miRNAs on CRPC tumor cells have the ability to suppress metastatic phenotypes. Conclusion miRNAs may have a growing role in CRPC prognostication and potentially transform into a therapeutic potential.

IntroductionPeyronie's disease (PD) and Dupuytren contractures (DC) are often comorbid and are believed to have a similar underlying pathophysiologic mechanism.AimTo investigate the prevalence of PD-like symptoms (PDLS) in men with DC.MethodsFrom October 2013 to December 2016, men who were seen and evaluated for DC were offered the opportunity to participate in an anonymous survey. The survey assessed several basic demographic and sexual health factors and included items from the International Index of Erectile Function and the Erection Hardness Scale. Men who reported PDLS were asked a series of questions derived from the Peyronie's Disease Questionnaire and for their opinions on theoretical treatment modalities for sexual problems and penile deformity.Main Outcome MeasurePrevalence of PDLS in men with DC.ResultsOne hundred forty men with DC were invited to participate; 85 surveys were returned (response rate = 61%). Twenty-two respondents (26%, 95% confidence interval = 17–35) reported PDLS. Approximately one fourth of all respondents had an Erection Hardness Scale score lower than 3. The most common specific PDLS concerns were penile curvature (91%), length loss (55%), narrowing (36%), and hinging (32%). In men with PDLS, 73% felt at least a little bothered by the symptoms when attempting sexual activity and 40% reported having sex less frequently because of the symptoms. Just 27% of men with PDLS had ever used a treatment for a sexual concern. In terms of treatments for penile deformities, 64% of men with PDLS expressed an interest in treatment administered in the form of an in-office procedure; 41% were potentially amenable to a surgical procedure.ConclusionThe prevalence of PDLS in men with DC is similar to the prevalence of DC in men diagnosed with PD. A substantial number of these men have distress and would consider standard-of-care treatments for PD.Shindel AW, Sweet G, Thieu W, et al. Prevalence of Peyronie's Disease-Like Symptoms in Men Presenting With Dupuytren Contractures. Sex Med 2017;5:e135–e141.