Mapping the Active Site Helix-to-Strand Conversion of CxxxxC Peroxiredoxin Q Enzymes

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• 作者：Arden Perkins ; Michael C. Gretes ; Kimberly J. Nelson ; Leslie B. Poole ; P. Andrew Karplus
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：September 25, 2012
• 年：2012
• 卷：51
• 期：38
• 页码：7638-7650
• 全文大小：840K
• 年卷期：v.51,no.38(September 25, 2012)
• ISSN：1520-4995

文摘

Peroxiredoxins (Prx) make up a family of enzymes that reduce peroxides using a peroxidatic cysteine residue; among these, members of the PrxQ subfamily are proposed to be the most ancestral-like yet are among the least characterized. In many PrxQ enzymes, a second 鈥渞esolving鈥?cysteine is located five residues downstream from the peroxidatic Cys, and these residues form a disulfide during the catalytic cycle. Here, we describe three hyperthermophilic PrxQ crystal structures originally determined by the RIKEN structural genomics group. We reprocessed the diffraction data and conducted further refinement to yield models with R_free values lowered by 2.3鈥?.2% and resolution extended by 0.2鈥?.3 脜, making one, at 1.4 脜, one of the best resolved peroxiredoxins to date. Comparisons of two matched thiol and disulfide forms reveal that the active site conformational change required for disulfide formation involves a transition of 20 residues from a pair of 伪-helices to a 尾-hairpin and 3₁₀-helix. Each conformation has 10 residues with a high level of disorder providing slack that allows the dramatic shift, and the two conformations are anchored to the protein core by distinct nonpolar side chains that fill three hydrophobic pockets. Sequence conservation patterns confirm the importance of these and a few additional residues for function. From a broader perspective, this study raises the provocative question of how to make use of the valuable information in the Protein Data Bank generated by structural genomics projects but not described in the literature, perhaps remaining unrecognized and certainly underutilized.