Intersubunit interactions in proton-translocating adenosine triphosphatase as revealed by hydrogen-exchange kinetics

Abstract

The rates of hydrogen-deuterium exchange in the peptide groups of the .alpha.- and .beta.-subunits and the .alpha.-.beta. subunit complex of proton-translocating ATPase from the thermophilic bacterium PS3 were examined. The exchange was much slower in the isolated .beta.-subunit than in the isolated .alpha.-subunit. This was taken as indicating that the structure of the .beta.-subunit is tighter than that of the .alpha.-subunit. ATP causes tightening of a relatively tight portion of the .alpha.-subunit and of a relatively loose portion of the .beta.-subunit. When the .alpha.- and .beta.-subunits are brought into contact, tightening of the .alpha.-subunit, but not the .beta.-subunit, occurs. The effect of ATP on the sturcture of the .beta.-subunit is more pronounced in the presence of the .alpha.-subunit than in its absence. The .alpha.-subunit has an allosteric site and the .beta.-subunit a catalytic site; the conformation of the .beta.-subunit is controlled by the .alpha.-subunit.