Cytochrome f
From Biocrawler, the free encyclopedia.
Cytochrome f is the largest subunit of cytochrome b6f complex (plastoquinol—plastocyanin reductase; EC 1.10.99.1 (http://www.expasy.org/cgi-bin/get-enzyme-entry?1.10.99.1)). The crystal structures of soluble (lumen-side) domain of cytochrome f reveal two structural domains: a small one above a larger one which, in turn, is on top of the attachment to the membrane domain. The large domain consists of an antiparallel β-sandwich and a short heme-binding peptide, which form a three-layer structure. The small domain is inserted between two β-strands of the large domain and is an all-β domain.
The heme is bound between two short helices at the N-terminus of cytochrome f. Within the second helix is the sequence motif for the c-type cytochromes, Cys-Xaa-Xaa-Cys-His, which is covalently attached to the heme through thioether bonds of the two cysteine residues. The fifth heme iron ligand is histidine and the sixth heme iron ligand is the α-amino group of N-terminal tyrosine residue (Tyr-1).
Cytochrome f has an internal network of water molecules. It has been hypothesized that this water chain functions as a proton wire. The water chain appears to be a conserved feature of cytochromes f.
References
- Cramer, W.A., Martinez, S.E., Huang, D., Tae, G.S., Everly, R.M., Heymann, J.B., Cheng, R.H., Baker, T.S. and Smith, J.L. (1994). "Structural aspects of the cytochrome b6f complex; structure of the lumen-side domain of cytochrome f". J. Bioenerg. Biomembr., 26, 31–47.
- Martinez, S.E., Huang, D., Ponomarev, M., Cramer, W.A. and Smith, J.L. (1996). "The heme redox center of chloroplast cytochrome f is linked to a buried five-water chain". Protein Science, 5, 1081–1092.
- Prince, R.C. and George, G.N. (1995). "Cytochrome f revealed". Trends Biochem. Sci., 20, 217–218.
External links
- 1CTM (http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1CTM) - PDB structure of lumen-side domain of cytochrome f from turnip (Brassica rapa)
- 1CFM (http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1CFM) - PDB structure of lumen-side domain of cytochrome f from Chlamydomonas reinhardtii
- 1CI3 (http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1CI3) - PDB structure of soluble domain of cytochrome f from Phormidium laminosum
- IPR002325 (http://www.ebi.ac.uk/interpro/IEntry?ac=IPR002325) - InterPro (http://www.ebi.ac.uk/interpro/) entry for cytochrome f
