| Symbol: | Apocytochr_F_C |
| Apocytochr_F_C | |
| Pfam: | PF01333 |
| Pfam Clan: | CL0105 |
| Interpro: | IPR002325 |
| Prosite: | PDOC00169 |
| Scop: | 1ctm |
| Tcdb: | 3.D.3 |
| Opm Family: | 92 |
| Opm Protein: | 3h1j |
Cytochrome f is the largest subunit of cytochrome b6f complex (plastoquinol - plastocyanin reductase;). In its structure and functions, the cytochrome b6f complex bears extensive analogy to the cytochrome bc1 complex of mitochondria and photosynthetic purple bacteria. Cytochrome f (cyt f) plays a role analogous to that of cytochrome c1, in spite of their different structures.[1]
The 3D structure of Brassica rapa (Turnip) cyt f has been determined.[2] The lumen-side segment of cyt f includes two structural domains: a small one above a larger one that, in turn, is on top of the attachment to the membrane domain. The large domain consists of an anti-parallel beta-sandwich and a short haem-binding peptide, which form a three-layer structure. The small domain is inserted between beta-strands F and G of the large domain and is an all-beta domain. The haem nestles between two short helices at the N terminus of cyt f. Within the second helix is the sequence motif for the c-type cytochromes, CxxCH (residues 21–25), which is covalently attached to the haem through thioether bonds to Cys-21 and Cys-24. His-25 is the fifth haem iron ligand. The sixth haem iron ligand is the alpha-amino group of Tyr-1 in the first helix.[2] Cyt f has an internal network of water molecules that may function as a proton wire.[2] The water chain appears to be a conserved feature of cyt f.