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Title

Redox- and pH-linked conformational changes in triheme cytochrome PpcA from Geobacter sulfurreducens

AuthorsMorgado, L.; Bruix, M. ; Pokkuluri, P. R.; Salgueiro, C. A.; Turner, D. L.
Issue Date2017
PublisherPortland Press
CitationBiochemical Journal 474: 231- 246 (2017)
AbstractThe periplasmic triheme cytochrome PpcA from Geobacter sulfurreducens is highly abundant; it is the likely reservoir of electrons to the outer surface to assist the reduction of extracellular terminal acceptors; these include insoluble metal oxides in natural habitats and electrode surfaces from which electricity can be harvested. A detailed thermodynamic characterization of PpcA showed that it has an important redox-Bohr effect that might implicate the protein in e/H coupling mechanisms to sustain cellular growth. This functional mechanism requires control of both the redox state and the protonation state. In the present study, isotope-labeled PpcA was produced and the three-dimensional structure of PpcA in the oxidized form was determined by NMR. This is the first solution structure of a G. sulfurreducens cytochrome in the oxidized state. The comparison of oxidized and reduced structures revealed that the heme I axial ligand geometry changed and there were other significant changes in the segments near heme I. The pH-linked conformational rearrangements observed in the vicinity of the redox-Bohr center, both in the oxidized and reduced structures, constitute the structural basis for the differences observed in the pK values of the redox-Bohr center, providing insights into the e/H coupling molecular mechanisms driven by PpcA in G. sulfurreducens.
URIhttp://hdl.handle.net/10261/162594
Identifiersdoi: 10.1042/BCJ20160932
issn: 1470-8728
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