The heterogeneous interaction of substoichiometric TNP-ATP and F1-ATPase from Escherichia coli.
The interactions of substoichiometric TNP-ATP and F1-ATPase from Escherichia coli (EF1) were examined and compared with those in the case of mitochondrial F1-ATPase (MF1) and F1-ATPase from thermophilic Bacillus PS3 (TF1). EF1 hydrolyzed substoichiometric TNP-ATP faster than TF1 or MF1, although some 20% of the TNP-ATP remained unhydrolyzed even in the presence of excess chase ATP. The affinity of the catalytic site of EF1 for the product, TNP-ADP, was weaker than that of TF1 or MF1, and the TNP-ADP was readily released upon addition of excess ATP. The amplitude of the difference absorption spectrum induced by binding of TNP-AT(D)P to EF1 was smaller than that of MF1 or TF1 under similar experimental conditions. When an excess amount of TNP-ATP was added to EF1 and the change of the difference spectrum was measured, the shape of the difference spectrum of the ATP-replaceable fraction was very similar to that in the case of binding of TNP-ATP to the isolated beta subunit of TF1, indicating that the rapidly replaceable fraction of bound TNP-ATP was actually at the catalytic site and most of the non-replaceable portion was bound at noncatalytic sites. Weaker affinity of the catalytic site for TNP-ATP may account for the heterogeneous binding and hydrolysis under the conditions described in this paper.
Muneyuki
E
E
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, Yokohama. emuneyuk@res.titech.ac.jp
Hisabori
T
T
Sasayama
T
T
Mochizuki
K
K
Yoshida
M
M
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D004926:Escherichia coli; D005456:Fluorescent Dyes / Q000378:metabolism*; D006868:Hydrolysis; D006180:Proton-Translocating ATPases / Q000378:metabolism*
D005456:Fluorescent Dyes; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases