2fw5
From Proteopedia
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Diheme cytochrome c from Rhodobacter sphaeroides
Overview
The diheme cytochrome c (DHC) from Rhodobacter sphaeroides is a soluble, protein with a mass of 16 kDa that represents a new class of c-type, cytochrome [Vandenberghe, I., et al. (1998) Biochemistry 37, 13075-13081]., The gene encoding DHC is associated with another encoding a cytochrome, known as SHP (sphaeroides heme protein). It is believed that DHC is the, electron donor for SHP, which is known to bind oxygen. To gain further, insight into the properties and role of DHC, we have carried out, structure-function studies on the protein and examined its interaction, with SHP. The crystal structures of native and recombinant DHC have been, determined to resolutions of 1.85 and 2.0 A, respectively. The structures, show that DHC folds into two distinct domains each containing one heme., While the N-terminal domain is a class I cytochrome c, the C-terminal, domain shows no similarity to any existing structures and thus constitutes, a novel cytochrome c structural motif. The shortest, edge-to-edge, distance between the heme groups is 10.2 A, and this distance is bridged, by Tyr31, thus ensuring fast internal electron transfer. DHC binds, strongly to its proposed physiological partner, SHP (K(d) = 0.26 microM in, 10 mM HEPES at pH 7.2 and 25 degrees C). However, at higher salt, concentrations, the binding becomes much weaker, indicating the importance, of electrostatic interactions. DHC is also very efficient in electron, transfer to SHP with a second-order rate constant of 1.8 x 10(7) M(-)(1), s(-)(1) (at pH 7.2, 10 degrees C, and I = 500 mM). The reduction, potentials of DHC and SHP are also suitably ordered for a favorable, reaction with the hemes of DHC showing potentials of -310 and -240 mV, respectively, and that for SHP being -105 mV. These potentials are, unaltered upon complex formation.
About this Structure
2FW5 is a Single protein structure of sequence from Rhodobacter sphaeroides with as ligand. Full crystallographic information is available from OCA.
Reference
Structural and functional studies on DHC, the diheme cytochrome c from Rhodobacter sphaeroides, and its interaction with SHP, the sphaeroides heme protein., Gibson HR, Mowat CG, Miles CS, Li BR, Leys D, Reid GA, Chapman SK, Biochemistry. 2006 May 23;45(20):6363-71. PMID:16700547
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