title: Cytochromes c': Structure, Reactivity and Relevance to Haem-Based Gas Sensing.
abstract: Cytochromes c' are a group of class IIa cytochromes with pentacoordinate haem centres and are found in photosynthetic, denitrifying and methanotrophic bacteria. Their function remains unclear, although roles in nitric oxide (NO) trafficking during denitrification or in cellular defence against nitrosoative stress have been proposed. Cytochromes c' are typically dimeric with each c-type haem-containing monomer folding as a four-α-helix bundle. Their hydrophobic and crowded distal sites impose severe restrictions on the binding of distal ligands, including diatomic gases. By contrast, NO binds to the proximal haem face in a similar manner to that of the eukaryotic NO sensor, soluble guanylate cyclase and bacterial analogues. In this review, we focus on how structural features of cytochromes c' influence haem spectroscopy and reactivity with NO, CO and O2. We also discuss the relevance of cytochrome c' to understanding the mechanisms of gas binding to haem-based sensor proteins.
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hough
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Oregon University, La Grande, Oregon, USA. Electronic address: candrew@eou.edu.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Andrew
mesh_terms: D001419:Bacteria / Q000201:enzymology*; D002248:Carbon Monoxide / Q000378:metabolism*; D045305:Cytochromes c' / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D008958:Models, Molecular; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013057:Spectrum Analysis
chemical_list: D045305:Cytochromes c'; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D010100:Oxygen
keywords: Carbon monoxide; Crystal structures; Gas sensor; Haem protein; Kinetics; Nitric oxide; Resonance Raman; Spectroscopy