Investigation of subunit interactions by radiation inactivation: the case of Na+/K+-ATPase

The target size of Na+/K+-ATPase has been determined by radiation inactivation. To interpret the results, we have performed Monte Carlo simulations of the inactivation process. This seems to be a general method for the interpretation of such studies. The simulation revealed that radiation inactivation can distinguish between monoprotomeric and multiprotomeric models of enzyme action only if the measured reaction requires the actual co-operation of, rather than the mere co-existence of, different protomeres.