Nucleotide binding sites on beef heart mitochondrial F1-ATPase. Cooperative interactions between sites and specificity of noncatalytic sites

We have studied the properties of beef heart mitochondrial F1 having inhibitory MgADP bound at one of the three catalytic sites and various levels of occupancy of the three noncatalytic nucleotide sites including zero, two, or three ADP/ATPs or two ADP/ATP plus one GTP. The properties examined inclu...

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Bibliographic Details
Published in:The Journal of biological chemistry 1993-11, Vol.268 (31), p.23179-23185
Main Authors: MILGROM, Y. M, CROSS, R. L
Format: Article
Language:English
Subjects:
Adenosine Diphosphate - metabolism
Adenosine Triphosphate - metabolism
Allosteric Regulation
Analytical, structural and metabolic biochemistry
Animals
Binding Sites
Biological and medical sciences
Cattle
Diphosphates - metabolism
Enzymes and enzyme inhibitors
Fundamental and applied biological sciences. Psychology
Guanosine Triphosphate - metabolism
Hydrolases
In Vitro Techniques
Mitochondria, Heart - metabolism
Proton-Translocating ATPases - metabolism
Ribonucleotides - metabolism
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Summary:We have studied the properties of beef heart mitochondrial F1 having inhibitory MgADP bound at one of the three catalytic sites and various levels of occupancy of the three noncatalytic nucleotide sites including zero, two, or three ADP/ATPs or two ADP/ATP plus one GTP. The properties examined include the rate of MgATP-dependent reactivation and the rate of increase in the fraction of F1 containing transiently bound intermediates. For each form of the enzyme tested, the rate of reactivation closely paralleled the rate of increase in the level of bound intermediates, indicating that when one catalytic site on F1 is blocked by inhibitory MgADP, the remaining two sites are incapable of residual uni- or bi-site activity. It was also found that the stability of the MgADP-inhibited complex decreases with full occupancy of the noncatalytic sites. This demonstrates that the noncatalytic sites modulate the properties of catalytic sites. Finally, it was found that the noncatalytic sites on mitochondrial F1 do not, as has long been believed, bind adenine nucleotides exclusively. Evidence is presented that both GTP and PPi bind tightly at noncatalytic sites.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)49444-1