[Role of adenosine triphosphatase on nitrogenase function]

The decoupling possibility of ATPase reaction with electron transfer process in the time of nitrogenase photolysis by lambda 435 nm light has been established. The COOH and the possibility of imidazole groups have been revealed in nitrogenase ATPase centre by methods of chemical modification. The reaction of direct 18O-exchange between inorganic phosphate and medium water was discovered, proceeding under reverse hydrolysis of acylphosphate bond, formed by phosphorylation of COOH-group in ATPase centre. Direct 18O-exchange was shown to be stimulated by ATP and ADP, but to be insensitive to GTP, CTP, AMP-nucleotide which are not ATPase centre substrates. The coupling mechanism of ATPase reaction with electron transfer is suggested; it is based on the possibility of compulsory protonation of Fe-S-cluster at the expense of proton transfer from the imidazole site, facilitating additional electron transfer under "superreduction" of nitrogenase component of the Mo-Fe-protein. It is assumed that this protonation is initiated by COOH-group of charge relay transfer with imidasole fragment.