Cross-linking studies on the 50 S ribosomal subunit of Escherichia coli with methyl 4-mercaptobutyrimidate.

The 50 S ribosomal subunits of Escherichia coli were incubated with methyl 4-mercaptobutyrimidate and the formation of intermolecular protein:protein disulfide bonds was promoted by oxidation. Cross-linked proteins were analyzed by diagonal polyacrylamide/sodium dodecyl sulfate gel electrophoresis. Three pairs of cross-linked proteins were identified: L2-L7,L12; L5-L7,L12; and L17-L32. The significance of the results in relation to the location of sites for factor binding, peptidyltransferase, and GTP hydrolysis is discussed.