1CTM image
Deposition Date 1994-01-02
Release Date 1994-05-31
Last Version Date 2024-10-16
Entry Detail
PDB ID:
1CTM
Title:
CRYSTAL STRUCTURE OF CHLOROPLAST CYTOCHROME F REVEALS A NOVEL CYTOCHROME FOLD AND UNEXPECTED HEME LIGATION
Biological Source:
Source Organism:
Brassica rapa (Taxon ID: 3711)
Method Details:
Experimental Method:
Resolution:
2.30 Å
R-Value Free:
0.27
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:CYTOCHROME F
Gene (Uniprot):petA
Chain IDs:A
Chain Length:250
Number of Molecules:1
Biological Source:Brassica rapa
Ligand Molecules
Primary Citation
Crystal structure of chloroplast cytochrome f reveals a novel cytochrome fold and unexpected heme ligation.
Structure 2 95 105 (1994)
PMID: 8081747 DOI: 10.1016/S0969-2126(00)00012-5

Abstact

BACKGROUND Cytochrome f is the high potential electron acceptor of the chloroplast cytochrome b6f complex, and is the electron donor to plastocyanin. The 285-residue cytochrome f subunit is anchored in the thylakoid membrane of the chloroplast by a single membrane-spanning segment near the carboxyl terminus. A soluble redox-active 252-residue lumen-side polypeptide with native spectroscopic and redox properties, missing the membrane anchor and carboxyl terminus, was purified from turnip chloroplasts for structural studies. RESULTS The crystal structure of cytochrome f, determined to 2.3 A resolution, has several unexpected features. The 252-residue polypeptide is organized into one large and one small domain. The larger heme-binding domain is strikingly different from known structures of other c-type cytochromes and has the same fold as the type III domain of the animal protein, fibronectin. Cytochrome f binds heme with an unprecedented axial heme iron ligand: the amino terminus of the polypeptide. CONCLUSION The first atomic structure of a subunit of either the cytochrome b6f complex or of the related cytochrome bc1 complex has been obtained. The structure of cytochrome f allows prediction of the approximate docking site of plastocyanin and should allow systematic studies of the mechanism of intra- and inter-protein electron transfer between the cytochrome heme and plastocyanin copper, which are approximately isopotential. The unprecedented axial heme iron ligand also provides information on the sequence of events (i.e. cleavage of signal peptide and ligation of heme) associated with translocation of the cytochrome across the membrane and its subsequent folding.

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Primary Citation of related structures