Reductive-Methylation Studies on L7 and L12 Ribosomal Proteins.

1. L7 and L12 ribosomal proteins were reductively methylated in isolation and in situ, i.e. bound to the 50-S ribosomal subunit. The peptide bonds involving the carboxyl groups of &epsi-N-methylated lysines are resistant to trypsin attack. 2. Comparison shows that most of the lysine residues of' L7 and L12 proteins are more reactive in situ than in isolation. A partial unfolding or reduced association in situ is proposed. Notably when modified in solution, the reactivity of the acetylated form (L7) was greater than that of the deacetylated from (L12). 3. After reductive methylation the L7 and L12 proteins remain active in the GTPase reaction dependent on elongation factor G. [ABSTRACT FROM AUTHOR]