Ribosomal Protein S1 Associates with Escherichia coli Ribosomal 30‐S Subunit by Means of Protein‐Protein Interactions

Abstract

Ribosomal proteins S1 when associated with the 30‐S subunit does not interact with 16‐S RNA but its binding is determined mostly by protein‐protein interactions. These conclusions are based on the following data. Ultraviolet irradiation (λ=254 nm) of the 30‐S subunit does not result in the covalent cross‐linking of S1 with 16‐S RNA at irradiation doses up to 150 quanta/nucleotide, whereas the irradiation under the same conditions of S1 · polynucleotide complexes [S1 · poly(U), S1 · poly(A) and S1 · Qβphage RNA] induces effective formation of polynucleotide‐protein cross‐links. Mild treatment of 30‐subunits lacking S‐1 with RNase A or with cobra venom endonuclease results in removal of 10–20%of the total nucleotide material but does not affect their sedimentation characteristics or their S1 binding capacity. The association of S1 with S1‐depleted 30‐S subunits is insensitive to aurintricarboxylic acid, which is known as a strong inhibitor of complex formation between S1 and polynucleotides. Mild trypsin treatment of S1‐depleted 30‐S subunits greatly reduces their S 1 binding capacity. Copyright © 1982, Wiley Blackwell. All rights reserved