3emp

Crystal Structure of the S-acetanilide modified form of C165S AhpC

spinqualitylabelsall models 3emp, resolution 4.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3emp is a 5 chain structure with sequence from Salmonella enterica subsp. enterica serovar Typhimurium. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 4Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function AHPC_SALTY Directly reduces alkyl hydroperoxides with the use of electrons donated by the 57 kDa flavoprotein alkyl hydroperoxide reductase. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Salmonella typhimurium AhpC is a founding member of the peroxiredoxin family, a ubiquitous group of cysteine-based peroxidases with high reactivity toward hydrogen peroxide, organic hydroperoxides, and peroxynitrite. For all of the peroxiredoxins, the catalytic cysteine, referred to as the peroxidatic cysteine (C(P)), acts as a nucleophile in attacking the peroxide substrate, forming a cysteine sulfenic acid at the active site. Because thiolates are far stronger nucleophiles than thiol groups, it is generally accepted that cysteine-based peroxidases should exhibit pK(a) values lower than an unperturbed value of 8.3-8.5. In this investigation, several independent approaches were used to assess the pK(a) of the two cysteinyl residues of AhpC. Methods using two different iodoacetamide derivatives yielded unperturbed pK(a) values (7.9-8.7) for both cysteines, apparently due to reactivity with the wrong conformation of C(P) (i.e., locally unfolded and flipped out of the active site), as supported by X-ray crystallographic analyses. A functional pK(a) of 5.94 +/- 0.10 presumably reflecting the titration of C(P) within the fully folded active site was obtained by measuring AhpC competition with horseradish peroxidase for hydrogen peroxide; this value is quite similar to that obtained by analyzing the pH dependence of the epsilon(240) of wild-type AhpC (5.84 +/- 0.02) and similar to those obtained for two typical 2-cysteine peroxiredoxins from Saccharomyces cerevisiae (5.4 and 6.0). Thus, the pK(a) value of AhpC balances the need for a deprotonated thiol (at pH 7, approximately 90% of the C(P) would be deprotonated) with the fact that thiolates with higher pK(a) values are stronger nucleophiles. Cysteine pK(a) values for the bacterial peroxiredoxin AhpC.,Nelson KJ, Parsonage D, Hall A, Karplus PA, Poole LB Biochemistry. 2008 Dec 2;47(48):12860-8. PMID:18986167 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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