ISSN:
1432-1327
Keywords:
Key words Nine-haem cytochrome c
;
Multiple wavelength anomalous dispersion phasing method
;
Sulfate-reducing bacteria
;
Electron transfer
;
Modelling and interaction studies
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract A monomeric nine-haem cytochrome c (9Hcc) with 292 amino acid residues was isolated from cells of the sulfate- and nitrate-reducing bacterium Desulfovibrio desulfuricans ATCC 27774 grown under both nitrate- and sulfate-respiring conditions. The nucleotide sequence encoding the 292 residues was determined, allowing the correction of about 10% of the previous primary structure, determined from 1.8 Å electron density maps. The refinement at 1.8 Å resolution of the structural model was completed, giving an R-value of 16.5%. The nine haem groups are arranged into two tetrahaem clusters, located at both ends of the molecule, with Fe-Fe distances and local protein fold very similar to tetrahaem cytochromes c 3, and the extra haem is located asymmetrically between the two regions. The new primary sequence determination confirmed the 39% sequence homology found between this cytochrome and the C-terminal region (residues 229–514) of the high-molecular-weight cytochrome c (Hmc) from D. vulgaris Hildenborough, providing strong evidence of structural similarity between 9Hcc and the C-terminal region of Hmc. The interaction between 9Hcc and the tetrahaem cytochrome c 3 from the same organism was studied by modelling methods, and the results suggest that a specific interaction is possible between haem 4 of tetrahaem cytochrome c 3 and haem 1 or haem 2 of 9Hcc, in agreement with previous kinetic experiments which showed the catalytic effect of the tetrahaem cytochrome c 3 upon the reduction of 9Hcc by the [NiFe] hydrogenase from D. desulfuricans ATCC 27774. These studies suggest a role for 9Hcc as part of the assembly of redox proteins involved in recycling the molecular hydrogen released by the cell as a result of substrate oxidation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050334
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