Chemical Modifications of Escherichia coli Ribosomal Proteins S4, S7, and S8 in Regard to Their Capacity for Binding 16 S RNA

Abstract

Mild specific chemical modifications were used to test the possible role of cysteines, tyrosines, and amino groups of ribosomal proteins S4, S7, and S8 for binding to 16 S RNA (Escherichia coli). The single cysteine residue present in proteins S4 and S8 is not directly involved in the binding process with RNA. The protein S7 does not contain cysteine. Total nitration of tyrosines in S4, S7, and S8 abolishes the binding capacity of these proteins. However, when the modification is done with the preformed protein–RNA complexes, some protection occurs. Two amino groups could be reacted in free S8 as well as in an S8–RNA complex. This modification does not influence protein–RNA interaction. Proteins S4, S7, and S8 in Regard to Their Capacity for Binding 16 S RNA. Can. J. Biochem. 52, modified. A new method for the stoichiometric determination of single protein–RNA complexes is presented.