Turkey cytochrome c oxidase contains subunit VIa of the liver type associated with low efficiency of energy transduction.
Cytochrome c oxidase was isolated from turkey liver, heart and breast skeletal muscle and separated by SDS/PAGE. The N-terminal amino-acid sequence of subunit VIa from all tissues and internal sequences from the skeletal muscle enzyme show homology to the mammalian liver-type subunit VIaL, which was verified by isolation and sequencing of the cDNA of turkey subunit VIa. No cDNA corresponding to subunit VIaH (mammalian heart-type) could be found by RACE-PCR with mRNA from all turkey tissues. Measurement of proton translocation with the reconstituted enzymes from turkey liver and heart revealed H+/e- ratios below 0.5 that were independent of the intraliposomal ATP/ADP ratio, as previously found with the bovine liver enzyme. Under identical conditions, the bovine heart enzyme revealed H+/e- ratios of 0.85 at low and 0.48 at high intraliposomal ATP/ADP ratios. The results suggest that in birds the lower H+/e-ratio of cytochrome c oxidase participates in elevated resting metabolic rate and thermogenesis.
Hüttemann
M
M
Fachbereich Chemie, Philipps-Universität, Marburg, Germany.
Arnold
S
S
Lee
I
I
Mühlenbein
N
N
Linder
D
D
Lottspeich
F
F
Kadenbach
B
B
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D004734:Energy Metabolism; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D014422:Turkeys
D017931:DNA Primers; D018076:DNA, Complementary; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV