TSRI's main web site PROMISE mirror at TSRI Metalloprotein DB site Created: 5 August 1996
Last modified: 1 February 1999

Cytochrome c1
Haem type Haem iron coordination Axial iron ligands Formal iron
oxidation/spin
states
Haem c image
Haem c
His-Haem-Met image
Hexacoordinate
NepsilonHis;

SdeltaMet

FeII (S=0);
FeIII (S=1/2)

Cytochrome c1 (cyt c1) is one of three redox subunits of the cytochrome bc1 complex (ubiquinol:ferricytochrome c oxidoreductase; EC 1.10.2.2) [1, 2]. In its structure and functions, the cyt bc1 complex bears extensive analogy to the cyt b6f complex of chloroplasts and cyanobacteria; cyt c1 plays a role analogous to that of cyt f, in spite of their different structures [3].

Most cyt c1 contain near the N­terminus the sequence motif typical of the c­type cytochromes: 

CxxCH
which is covalently attached to the haem through thioether bonds to Cys residues; His is the fifth haem iron ligand. (The Euglena gracilis cyt c1 lacks the first conserved Cys involved in haem linkage in other cyt c1 [4].) The sixth haem iron ligand is provided by a Met residue [5].

Mitochondrial cyt c1 is anchored in the membrane by one membrane­spanning segment near the C­terminus. A water­soluble cyt c1 preparation can be obtained by removing the C­terminal hydrophobic stretch [6, 7]. The water­soluble cyt c1 cannot be assembled into the bc1 complex, but displays essentially the same spectroscopic properties as the native protein, and is able to transfer electrons to cyt c [1].

3­D structures of the cyt bc1 complex from mitochondria have been determined [2 and references therein]. Cyt c1 is an all­alpha protein resembling Class I cytochromes c. In bovine cyt c1, the haem iron is coordinated by His­41 and Met­160, and the haem is covalently bound to Cys­37 and Cys­40. Cyt c1 contains a number of insertions and deletions between helices as compared to a Class I cyt c. Structural differences are apparently related to the specific cyt c1-protein interactions [8].

Cytochrome c1 in motif databases

PRINTS ID PRINTS AC PROSITE/BLOCKS ID PROSITE AC BLOCKS AC
CYTOCHROMEC1 PR00603 CYTOCHROME_C PS00190 BL00190

Cytochromes c1 in alignment databases

Protein Superfamily Protein Homology Domain Pfam LPFC 3­D alignment
00003; cytochrome c1 heme protein 00189; cytochrome c1 heme protein
-
-

Cytochrome c1 in 3­D databases

Cytochrome bc1 complex contains two haem b groups, one haem c and one [Fe2S2] cluster per monomer.

PDB scop BSMRELI
Base		 Header MMS Abstract ¹
1bcc
-
 1bcc
-
 Cytochrome bc1 complex (complex with ubiquinone­10, phosphatidyl ethanolamine and B­octylglucoside); chicken (heart mitochondrial)
-
1be3
-
 1be3
-
 Cytochrome bc1 complex; bovine (heart mitochondrial)
-
1bgy
-
 1bgy
-
 Cytochrome bc1 complex; bovine (heart mitochondrial)
-
1qcr
-
 1qcr
-
 Cytochrome bc1 complex (Calpha atoms only); bovine (heart mitochondrial)
-
3bcc
-
 3bcc
-
 Cytochrome bc1 complex (complex with stigmatellin and antimycin); chicken (heart mitochondrial)
-

¹ Macromolecular Structures abstract. Full text is available to BioMedNet Members

References

  1. Bechmann, G., Schulte, U. and Weiss, H. (1992) Mitochondrial ubiquinol-cytochrome c oxidoreductase. In Ernster, L., Ed. Molecular Mechanisms in Bioenergetics. Elsevier, Amsterdam, pp. 199-216.
  2. Crofts, A.R. and Berry, E.A. (1998) Structure and function of the cytochrome bc1 complex of mitochondria and photosynthetic bacteria. Curr. Opin. Struct. Biol. 8, 501-509.
  3. Prince, R.C. and George, G.N. (1995) Cytochrome f revealed. Trends Biochem. Sci. 20, 217-218.
  4. Mukai, K., Yoshida, M., Toyosaki, H., Yao, Y., Wakabayashi, S. and Matsubara, H. (1989) An atypical heme­binding structure of cytochrome c1 of Euglena gracilis mitochondrial complex III. Eur. J. Biochem. 178, 649-656.
  5. Gray, K.A., Davidson, E. and Daldal, F. (1992) Mutagenesis of methionine­183 drastically affects the physicochemical properties of cytochrome c1 of the bc1 complex of Rhodobacter capsulatus. Biochemistry 31, 11864-11873.
  6. Li, Y., Leonard, K. and Weiss, H. (1981) Membrane­bound and water­soluble cytochrome c1 from Neurospora mitochondria. Eur. J. Biochem. 116, 199-205.
  7. Hase, T., Harabayashi, M., Kawai, K. and Matsubara, H. (1987) A carboxyl­terminal hydrophobic region of yeast cytochrome c1 is necessary for functional assembly into complex III of the respiratory chain. J. Biochem. (Tokyo) 102, 411-419.
  8. Iwata, S., Lee, J.W., Okada, K., Lee, J.K., Iwata, M., Rasmussen, B., Link, T.A., Ramaswamy, S. and Jap, B.K. (1998) Complete structure of the 11­subunit bovine mitochondrial cytochrome bc1 complex. Science 281, 64-71.
Bibliography on structural studies of cytochrome c1
Bibliography on structural studies of cytochrome bc1 complex
Reviews on cytochrome bc1 complex