Allosteric properties of cyanobacterial cytochrome c oxidase: inhibition of the coupled enzyme by ATP and stimulation by ADP.
Thorough analysis of the cta operon of Synechocystis sp. PCC6803 (grown in high-concentration salt medium to enhance the expression of respiratory proteins) showed that, apart from ctaCDE and Fb genes potentially encoding subunits I, II, III, and a small pseudo-bacteria-like subunit-IV of unknown function, a large mitochondria-like cta-Fm gene and a pronounced terminator structure are additional components of the operon. The deduced cta Fm gene product shows approximately 50% and 20% sequence identity to the Saccharomyces cerevisiae and beef heart mitochondrial COIV proteins, respectively. It also shows amino acid regions (near the N terminus, on the cytosolic side) with conspicuous sequence similarities to adenylate-binding proteins such as ATP synthase beta subunit Walker A and B consensus regions or to adenylate kinase. We suggest that, similar to the situation with beef heart mitochondria, it is the mitochondria-like subunit-IV of the cyanobacterial aa3-type cytochrome-c oxidase that confers allosteric properties to the cyanobacterial enzyme, the H+/e- ratios of cytochrome c oxidation being significantly lowered by ATP (intravesicular or intraliposomal) but enhanced by ADP. Therefore, the antagonistic action of ATP and ADP was in a way that the redox reaction proper, was always significantly less affected than the coupled proton translocation. Evolutionary and ecological implications of the unusual allosteric regulation of a prokaryotic cytochrome-c oxidase is discussed.
Alge
D
D
Molecular Bioenergetics Group, Institute of Physical Chemistry, University of Vienna, Austria.
Wastyn
M
M
Mayer
C
C
Jungwirth
C
C
Zimmermann
U
U
Zoder
R
R
Fromwald
S
S
Peschek
G A
GA
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000494:Allosteric Regulation / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009876:Operon; D017386:Sequence Homology, Amino Acid
D004269:DNA, Bacterial; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV