Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the E.coli 70S ribosome in the initiation state it has been modeled to contact the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; bridge B1a is broken in the model with bound EF-G, while the protein-protein contacts between S13 and L5 in B1b change. Contacts the tRNAs in the A and P sites (By similarity). Part of the 30S ribosomal subunit. Forms a loose heterodimer with protein S19. Cross-links to the P site tRNA and weakly to the A site tRNA. Forms two bridges to the 50S subunit in the 70S ribosome, contacting the 16S rRNA and protein L5 (By similarity). Belongs to the universal ribosomal protein uS13 family.