Rhodobacter sphaeroides haem protein: a novel cytochrome with nitric oxide dioxygenase activity.

Abstract

Rhodobacter sphaeroides produces a novel cytochrome, designated as SHP (sphaeroides haem protein), that is unusual in having asparagine as a redox-labile haem ligand. The gene encoding SHP is contained within an operon that also encodes a DHC (dihaem cytochrome c) and a membrane-associated cytochrome b. DHC and SHP have been shown to have high affinity for each other at low ionic strength (Kd=0.2 microM), and DHC is able to reduce SHP very rapidly. The reduced form of the protein, SHP2+ (reduced or ferrous SHP), has high affinity for both oxygen and nitric oxide (NO). It has been shown that the oxyferrous form, SHP2+-O2 (oxygen-bound form of SHP), reacts rapidly with NO to produce nitrate, whereas SHP2+-NO (the NO-bound form of SHP) will react with superoxide with the same product formed. It is therefore possible that SHP functions physiologically as a nitric oxide dioxygenase, protecting the organism against NO poisoning, and we propose a possible mechanism for this process.

• Authors: Bor-Ran Li, J L Ross Anderson, Christopher G Mowat, Caroline S Miles, Graeme A Reid, Stephen K Chapman
• Journal: Biochemical Society transactions (Biochem Soc Trans) Vol. 36 Issue Pt 5 Pg. 992-5 (Oct 2008) ISSN: 0300-5127 [Print] England
• PMID: 18793176 (Publication Type: Journal Article)

Chemical References

• Bacterial Proteins
• Cytochrome c Group
• Hemeproteins
• Nitrates
• SHP protein, Rhodobacter sphaeroides
• Superoxides
• Nitric Oxide
• Oxygenases
• nitric oxide dioxygenase
• Oxygen

Topics

• Bacterial Proteins (chemistry, metabolism)
• Cytochrome c Group (chemistry, metabolism)
• Hemeproteins (chemistry, metabolism)
• Models, Molecular
• Molecular Structure
• Nitrates (metabolism)
• Nitric Oxide (metabolism)
• Oxygen (metabolism)
• Oxygenases (chemistry, metabolism)
• Protein Structure, Tertiary
• Rhodobacter sphaeroides (chemistry, enzymology)
• Superoxides (metabolism)