Chemical and Physical Characterization of the Activation of Ribulosebisphosphate Carboxylase/oxygenase

Ribulosebisphosphate carboxylase/oxygenase requires CO2 and Mĝ "*" for activation; CO2 reacts with a protein e-amino group to form a carbamate which is stabilized by binding of Mg2+. In the case of the hexadecameric enzyme from spinach, the site of carbamate formation is Lys-201 (Lorimer, 1981). The enzyme from Atoatigenes eutrophuSj also hexadecameric, undergoes a substantial change in conformation upon activation as reflected by a decrease in S20 w from 17.5 S to 14.3 S (Bowien, Gottschalk, 1982). To assess the generality of these aspects of activation we have characterized the site of carbamate formation in the carboxylase from RhodospiriZttim rubmrrt^ a dimeric enzyme, and have examined the shapes of the activated and deactivated forms of the spinach and R. rubvum enzymes in solution by small angle neutron scattering.