Characterization of the Region on Protein L7/L12 Involved in Binding to Ribosomal Particles

Abstract

Tryptic digestion of reductively methylated protein L7/L12 [from Escherichia coli] yields a large tryptic fragment, which comprises amino acids 1-59. At the most, 2 molecules of this fragment can bind to a 50 S ribosomal particle deprived of protein L7/L12. Besides, binding of each single 1-59 fragment competes with binding of 1 dimeric L7/L12 molecule. MW studies on the fragment reveal a monomeric structure. Digestion of the 1-59 fragment with carboxypeptidase Y leads to the formation of a 1-55 fragment. The binding characteristics of the latter fragment are similar to those of the 1-59 fragment. A monomeric stretch of L7/L12, comprising the first 55 amino acids, is apparently sufficient for attaching L7/L12 to the ribosome.