1rcp
CYTOCHROME C'
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OverviewOverview
The structures of two polymorphs of cytochrome c' from Rhodobacter, capsulatus (RCCP) strain M110 have been determined by the molecular, replacement method. Iron anomalous scattering data were used to confirm, the molecular replacement solution. The structures were refined at 1.72, angstrom and 2.0 angstrom resolution to R-values of 15.0% and 16.3%, respectively. The RCCP molecule is a dimer and each of the identical 129, residue subunits folds as a four-helical bundle with a covalently bound, heme group in the center. This structural motif resembles that of, cytochromes c' reported from Rhodospirillum molischianum (RMCP), Rhodospirillum rubrum (RRCP), Chromatium vinosum (CVCP), Achromobacter, xyloseoxidans (AXCP) and Alcaligenes denitrificans (ADCP). However, the, architecture of the RCCP dimer, that is, the mode of association of, subunits, differs substantially from that of the other cytochromes c'. In, the RCCP dimer, the subunits are roughly parallel with each other and only, helix B of each subunit participates in formation of the dimer interface., Measurement of the solvent-accessible surface area indicates that the, dimer interface is smaller in RCCP than in the other cytochromes c'. In, RMCP, CVCP, RRCP, AXCP and ADCP the subunits cross each other to form an X, shape, and two helices, A and B, of each subunit interact across the dimer, interface. These results are consistent with hydrodynamic measurements, which show that there is an equilibrium between monomers and dimer in, RCCP, whereas the dimer is the predominant form in the other cytochromes, c' for which structures have been determined. Structural comparison of the, six cytochromes c' reveal that they can be divided into two groups. In, group 1 cytochromes c', CVCP and RCCP, the amino acid sequences and the, folding of subunits are arranged in such a way as to allow the formation, of a deep channel between helices B and C with direct solvent, accessibility to the heme sixth ligand position. There is no such channel, in group 2 cytochromes c', RMCP, RRCP, AXCP and ADCP. This may account, in, part, for the differences in carbon monoxide binding.
About this StructureAbout this Structure
1RCP is a Single protein structure of sequence from Rhodobacter capsulatus with HEM as ligand. Full crystallographic information is available from OCA.
ReferenceReference
High-resolution crystal structures of two polymorphs of cytochrome c' from the purple phototrophic bacterium rhodobacter capsulatus., Tahirov TH, Misaki S, Meyer TE, Cusanovich MA, Higuchi Y, Yasuoka N, J Mol Biol. 1996 Jun 14;259(3):467-79. PMID:8676382
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