Multiheme cytochromes c (cyts c) are c-type cyts characterized by non-standard structural and spectroscopic properties. The relative disposition of the heme cofactors in the core of these proteins is conserved and they can be classified from their geometry in two main groups ...
Multiheme cytochromes c (cyts c) are c-type cyts characterized by non-standard structural and spectroscopic properties. The relative disposition of the heme cofactors in the core of these proteins is conserved and they can be classified from their geometry in two main groups. In one group the porphyrin planes are arranged in a perpendicular fashion, while in the other they are parallel. Orientation of the heme groups is a key factor that regulates the intramolecular electron transfer pathway. A 16.5 kDa diheme cyt c, isolated from the bacterium Shewanella baltica OS155 (Sb-DHC), was cloned and expressed in E. coli and its structure was investigated by X-ray crystallography. Using high-resolution data (1.14 Å) collected at ELETTRA (Trieste), the crystal structure, with an orthorhombic cell (a = 40.81, b = 42.97, c = 82.07 Å), was solved using the homologous diheme from Rhodobacter sphaeroides (Rs-DHC) as the initial model. The electron density map of the refined structure (Rfact of 13.8% and Rfree of 15.4%) shows a two domain structure connected by a central unstructured region (N72-G87). The Sb-DHC, like its homologue (Rs-DHC), folds into a new cyt c class: the N-terminal globular domain, with its three α-helices, belongs to class I of c-type cyts, while the C-terminal domain includes a rare π-helix. The metal centre of the c-type heme groups is axially coordinated by two His residues and it is covalently bound to the protein through two Cys bonds.
Related Citations:
Cloning, expression, and physicochemical characterization of a new diheme cytochrome c from Shewanella baltica OS155. Di Rocco, G., Battistuzzi, G., Bortolotti, C.A., Borsari, M., Ferrari, E., Monari, S., Sola, M. (2011) J Biol Inorg Chem 16: 461
Structural and functional studies on DHC, the diheme cytochrome c from Rhodobacter sphaeroides, and its interaction with SHP, the sphaeroides heme protein. Gibson, H.R., Mowat, C.G., Miles, C.S., Li, B.R., Leys, D., Reid, G.A., Chapman, S.K. (2006) Biochemistry 45: 6363
Structural and biochemical characterization of DHC2, a novel diheme cytochrome c from Geobacter sulfurreducens. Heitmann, D., Einsle, O. (2005) Biochemistry 44: 12411
The 1.25 A resolution structure of the diheme NapB subunit of soluble nitrate reductase reveals a novel cytochrome c fold with a stacked heme arrangement. Brige, A., Leys, D., Meyer, T.E., Cusanovich, M.A., Van Beeumen, J.J. (2002) Biochemistry 41: 4827
Organizational Affiliation:
a Centre of Excellence in Biocrystallography (CEB), Department of Chemical and Pharmaceutical Sciences , University of Trieste , via L.Giorgieri 1, 34127 Trieste , Italy.
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