The C-terminal tail plays a role in the affinity of the 30S P site for different tRNAs. Mutations that decrease this affinity are suppressed in the 70S ribosome. Part of the 30S ribosomal subunit (PubMed:1091515, PubMed:7556101, PubMed:10094780, PubMed:12809609, PubMed:16272117, PubMed:27934701, PubMed:12244297, PubMed:27906160, PubMed:27906161, PubMed:28077875). Contacts 16S rRNA (PubMed:7556101). Cross-links to the P site tRNA and weakly to the A site tRNA (PubMed:8524654, PubMed:15308780). Belongs to the universal ribosomal protein uS9 family.