Binding sites for ribosomal proteins S8 and S15 in the 16 S RNA of Escherichia coli

Abstract

A fragment of the 16 S ribosomal RNA of Escherichia coli that contains the binding sites for proteins S8 and S15 of the 30 S ribosomal subunit has been isolated and characterized. The RNA fragment, which sediments at 5 S, was partially protected from pancreatic RNAase digestion when S15 alone, or S8 and S15 together, were bound to the 16 S RNA. Purified 5 S RNA was shown to reassociate specifically with protein S15 by analysis of binding stoichiometry. Although interaction between the fragment and protein S8 alone could not be detected, the 5 S RNA selectively bound both S8 and S15 when incubated with an unfractionated mixture of 30-S subunit proteins. Nucleotide sequence analysis demonstrated that the 5 S RNA arises from the middle of the 16 S RNA molecule and encompasses approximately 150 residues from Sections C, C′ 1 and C′ 2. Section C consists of a long hairpin loop with an extensively hydrogen-bonded stem and is contiguous with Section C′ 1. Sections C′ 1 and C′ 2, although not contiguous, are highly complementary and it is likely that together they comprise the base-paired stem of an adjacent loop.