Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; these bridges are implicated in subunit movement. Contacts the tRNAs in the A and P-sites. Part of the 30S ribosomal subunit. Forms a loose heterodimer with protein S19. Forms two bridges to the 50S subunit in the 70S ribosome. Belongs to the universal ribosomal protein uS13 family.