4mab

Publication Abstract from PubMed

The catalytic activity of peroxiredoxins (Prx), the dominant peroxidases in most organisms, requires a key cysteine in a substrate-ready fully folded (FF) conformation. This peroxidatic Cys is oxidized to sulfenic acid by the peroxide substrate, and then further reacts, after a local unfolding of the active site, to form a disulfide bond with a second 'resolving' Cys. For Salmonella typhimurium alkyl hydroperoxide reductase C (StAhpC) and some other Prxs, the FF structure is only known for an active site Cys-->Ser variant, and it is assumed that this variant accurately represents the wild type enzyme. Here, we have been able to determine the structure of authentic reduced wild type StAhpC by dithiothreitol treatment of crystals of a previously-solved disulfide form of the wild type enzyme. Structural comparisons allow us to define small, but real shifts in the active site and alterations to the dynamic properties that are caused by the Ser-mutation. We further characterize a linkage between the folding of the active site loop and C-terminal region and use this information to develop a strategy to crystallize the C165A variant (with the resolving Cys mutated to Ala) in the same crystal form. These data reveal how subtle modifications to Prx structures can substantially influence the enzymatic properties and that caution should be exercised in inferring wild type enzyme properties from the behavior of peroxidatic or resolving Cys mutants. We present a simple thermodynamic framework for rationalizing these impacts as well as those of physiologically-relevant regulatory posttranslational modifications and also propose a non-traditional strategy for designing selective Prx inhibitors.

Substrate-ready Conformation of Wild Type Salmonella typhimurium AhpC and the Sensitive Balance between Fully Folded and Locally Unfolded Conformations.,Perkins A, Nelson KJ, Williams JR, Parsonage D, Poole LB, Karplus PA Biochemistry. 2013 Oct 31. PMID:24175952^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.