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Publication Abstract from PubMed

The structure of dimeric cytochrome c(3) from the sulfate-reducing bacterium Desulfovibrio gigas, diDg, obtained by ab initio methods was further refined to 1.2 A resolution, giving final reliability factors of R(free) = 14.8% and R = 12.4%. This cytochrome is a dimer of tetraheme cytochrome c(3) molecules covalently linked by two solvent-accessible disulfide bridges, a characteristic unique to members of the cytochrome c(3) superfamily. Anisotropic analysis using the semi-rigid TLS method shows different behaviour for analogous loops in each monomer arising from their different packing environments. A detailed sequence and structural comparison with all other known cytochrome c(3) domains in single- and multi-domain cytochromes c(3) shows the presence of structurally conserved regions in this family, despite the high variability of the amino-acid sequence. An internal water molecule is conserved in a common structural arrangement in all c(3) tetraheme domains, indicating a probable electron-transfer pathway between hemes I and II. Unique features of diDg are an internal methionine residue close to heme I and to one of the axial ligands of heme III, where all other structures of the cytochrome c(3) superfamily have a phenylalanine, and a rather unusual CXXXCH heme-binding motif only found so far in this cytochrome.

Structure of dimeric cytochrome c3 from Desulfovibrio gigas at 1.2 A resolution.,Aragao D, Frazao C, Sieker L, Sheldrick GM, LeGall J, Carrondo MA Acta Crystallogr D Biol Crystallogr. 2003 Apr;59(Pt 4):644-53. Epub 2003, Mar 25. PMID:12657783^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.