1yex

Structural and biochemical analysis of the link between enzymatic activity and oligomerization in AhpC, a bacterial peroxiredoxin.

spinqualitylabelsall models 1yex, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1yex 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 2.3Å Ligands: SO4 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 Peroxiredoxins (Prxs) make up a ubiquitous class (proposed EC 1.11.1.15) of cysteine-dependent peroxidases with roles in oxidant protection and signal transduction. An intriguing biophysical property of typical 2-Cys Prxs is the redox-dependent modulation of their oligomeric state between decamers and dimers at physiological concentrations. The functional consequences of this linkage are unknown, but on the basis of structural considerations, we hypothesized that decamer-building (dimer-dimer) interactions serve to stabilize a loop that forms the peroxidatic active site. Here, we address this important issue by studying mutations of Thr77 at the decamer-building interface of AhpC from Salmonella typhimurium. Ultracentrifugation studies revealed that two of the substitutions (T77I and T77D) successfully disrupted the decamer, while the third (T77V) actually enhanced decamer stability. Crystal structures of the decameric forms of all three mutant proteins provide a rationale for their properties. A new assay allowed the first ever measurement of the true k(cat) and K(m) values of wild-type AhpC with H(2)O(2), placing the catalytic efficiency at 4 x 10(7) M(-)(1) s(-)(1). T77V had slightly higher activity than wild-type enzyme, and both T77I and T77D exhibited ca. 100-fold lower catalytic efficiency, indicating that the decameric structure is quite important for, but not essential to, activity. The interplay between decamer formation and active site loop dynamics is emphasized by a decreased susceptibility of T77I and T77D to peroxide-mediated inactivation, and by an increase in the crystallographic B-factors in the active site loop, rather than at the site of the mutation, in the T77D variant. Analysis of the link between enzymatic activity and oligomeric state in AhpC, a bacterial peroxiredoxin.,Parsonage D, Youngblood DS, Sarma GN, Wood ZA, Karplus PA, Poole LB Biochemistry. 2005 Aug 9;44(31):10583-92. PMID:16060667 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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