Monoclonal antibodies to epitopes in both C-terminal and N-terminal domains of Escherichia coli ribosomal protein L7/L12 inhibit elongation factor binding but not peptidyl transferase activity.

Two monoclonal antibodies against different epitopes in Escherichia coli ribosomal protein L7/L12, one within residues 74-120 and the other within residues 1-73, shown before to inhibit the binding of EF-G, have been tested for their effects on the binding to E. coli ribosomes of EF-Tu-aminoacyl-tRNA-GTP ternary complex and on peptidyl transferase activity. Both antibodies inhibit the binding of ternary complex and EF-Tu-dependent GTPase but have no inhibitory effect on peptidyl transferase activity. The inhibition of binding of both elongation factors is indicative of overlapping binding sites for EF-G and EF-Tu. The inhibition by both antibodies implies the contribution of both domains of L7/L12 to this binding site. This implies the location of one or more of the C-terminal domains of L7/L12 on the body of the 50S subunit. The absence of any inhibition of peptidyl transferase activity shows distinct separation of this site from the factor binding site.