One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the platform of the 30S subunit by binding and bridging several RNA helices of the 16S rRNA (PubMed:12809609, PubMed:16272117). Binds to its own mRNA, stabilizing it 5-UTR and preventing its translation (PubMed:24339747). In the E.coli 70S ribosome it has been modeled (PubMed:12809609) to contact the 23S rRNA of the 50S subunit forming part of bridge B4. In the two 3.5 A resolved ribosome structures (PubMed:16272117) there are minor differences between side-chain conformations. Part of the 30S ribosomal subunit (PubMed:776686, PubMed:10094780, PubMed:12244297, PubMed:12809609, PubMed:16272117, PubMed:27934701, PubMed:27906160, PubMed:27906161). Forms a bridge to the 50S subunit in the 70S ribosome, contacting the 23S rRNA (PubMed:12809609, PubMed:16272117). Part of the metY operon that extends to pnp, also has its own promoter (PubMed:2849753). Belongs to the universal ribosomal protein uS15 family.