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Solution structure of oxidized triheme cytochrome PpcA from Geobacter sulfurreducensSolution structure of oxidized triheme cytochrome PpcA from Geobacter sulfurreducens
Structural highlights
FunctionPublication Abstract from PubMedThe 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 pKa values of the redox-Bohr center, providing insights into the e-/H+ coupling molecular mechanisms driven by PpcA in G. sulfurreducens. Redox- and pH-linked conformational changes in triheme cytochrome PpcA from Geobacter sulfurreducens.,Morgado L, Bruix M, Pokkuluri PR, Salgueiro CA, Turner DL Biochem J. 2017 Jan 15;474(2):231-246. doi: 10.1042/BCJ20160932. Epub 2016 Nov, 14. PMID:28062839[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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