Insights into the alkyl peroxide reduction pathway of Xanthomonas campestris bacterioferritin comigratory protein from the trapped intermediate-ligand complex structures.
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Liao SJ, Yang CY, Chin KH, Wang AH, Chou SH
Insights into the alkyl peroxide reduction pathway of Xanthomonas campestris bacterioferritin comigratory protein from the trapped intermediate-ligand complex structures.
J Mol Biol. 2009 Jul 31;390(5):951-66. doi: 10.1016/j.jmb.2009.05.030. Epub 2009 May 25.
- PubMed ID
- 19477183 [ View in PubMed]
- Abstract
Considerable insights into the oxidoreduction activity of the Xanthomonas campestris bacterioferritin comigratory protein (XcBCP) have been obtained from trapped intermediate/ligand complex structures determined by X-ray crystallography. Multiple sequence alignment and enzyme assay indicate that XcBCP belongs to a subfamily of atypical 2-Cys peroxiredoxins (Prxs), containing a strictly conserved peroxidatic cysteine (C(P)48) and an unconserved resolving cysteine (C(R)84). Crystals at different states, i.e. Free_SH state, Intra_SS state, and Inter_SS state, were obtained by screening the XcBCP proteins from a double C48S/C84S mutant, a wild type, and a C48A mutant, respectively. A formate or an alkyl analog with two water molecules that mimic an alkyl peroxide substrate was found close to the active site of the Free_SH or Inter_SS state, respectively. Their global structures were found to contain a novel substrate-binding pocket capable of accommodating an alkyl chain of no less than 16 carbons. In addition, in the Intra_SS or Inter_SS state, substantial local unfolding or complete unfolding of the C(R)-helix was detected, with the C(P)-helix remaining essentially unchanged. This is in contrast to the earlier observation that the C(P)-helix exhibits local unfolding during disulfide bond formation in typical 2-Cys Prxs. These rich experimental data have enabled us to propose a pathway by which XcBCP carries out its oxidoreduction activity through the alternate opening and closing of the substrate entry channel and the disulfide-bond pocket.