1CYI: Cytochrome C6

The molecular structure of cytochrome c6 from the green alga Chlamydomonas reinhardtii has been determined from two crystal forms and refined to 1.9 A resolution. The two crystal forms are likely the result of different levels of post-translational modification of the protein. This is the first report of a high-resolution structure of a chloroplast-derived class I c-type cytochrome. The overall fold is similar to that of other class I c-type cytochromes, consisting of a series of alpha-helices and turns that envelop the heme prosthetic group. There is also a short two-stranded anti-parallel beta-sheet in the vicinity of the methionine axial ligand to the heme; this region of the molecule is formed by the most highly conserved residues in c6-type cytochromes. Although class I c-type cytochromes are assumed to function as monomers, both crystal forms of cytochrome c6 exhibit oligomerization about the heme crevice that is, in part, mediated by the short anti-parallel beta-sheet. The functional significance of this oligomerization is supported by the appearance of similar interfaces in other electron transfer couples, HPLC and light-scattering data, and is furthermore consistent with kinetic data on electron transfer reactions of c6-type cytochromes.
PDB ID: 1CYIDownload
MMDB ID: 55880
PDB Deposition Date: 1995/5/9
Updated in MMDB: 2011/11
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 1CYI: monomeric; determined by author
Molecular Components in 1CYI
Label Count Molecule
Protein (1 molecule)
Cytochrome C6(Gene symbol: CYC6)
Molecule annotation
Chemicals (5 molecules)
* Click molecule labels to explore molecular sequence information.

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