My watch list

Cytochrome f

Cytochrome f is the largest subunit of cytochrome b₆f complex (plastoquinol—plastocyanin reductase; EC 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.

Additional recommended knowledge

Recognize and detect the effects of electrostatic charges on your balance

Daily Visual Balance Check

What is the Correct Way to Check Repeatability in Balances?

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

Bendall, D.S. (2004). "The unfinished story of cytochrome f". Photosynth. Res. 80: 265–276. PMID 16328825.
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. PMID 8027021.
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. PMID 8762139.
Prince, R.C. and George, G.N. (1995). "Cytochrome f revealed". Trends Biochem. Sci. 20: 217–218. PMID 7631417.