Pseudomonas cytochrome c551 at 2.0 Å resolution: Enlargement of the cytochrome c family

Abstract

The structure of respiratory cytochrome C551 of P. aeruginosa, with 82 amino acids, has been solved by x-ray analysis and refined to a crystallographic R factor of 16.2%. It has the same basic folding pattern and hydrophobic heme environment as cytochromes c, c2, and c550 except for a large deletion at the bottom of the heme crevice. This same 'cytochrome fold' appears to be present in photosynthetic cytochromes c of green and purple sulfur bacteria, and algal cytochromes f, suggesting a common evolutionary origin for electron transport chains in photosynthesis and respiration.