Functional groups of elongation factor 2 involved in interactions with guanosine nucleotides and ribosomes.

Treatment of rat liver EF-2 with N-ethylmaleimide (MalNEt) did not affect the direct interactions of the factor with guanine nucleotides or with ribosomes, but inhibited the binding of guanosine 5'-(beta, gamma-methylene)triphosphate (GuoPP(CH2)P) to the EF-2-ribosome complex. The amino group reactive reagent 2,4,6-trinitrobenzenesulfonate (TNBS), however, inhibited specifically the direct interactions of EF-2 with guanine nucleotides, but not the binding of GuoPP(CH2)P to the EF-2-ribosome complex. The different sensitivities of EF-2 to MalNEt and to TNBS suggested that the binding sites involved in the binary vs. ternary complex might correspond to different conformational states or might even be distinct physical entities.