With S4 and S12 plays an important role in translational accuracy. Many suppressors of streptomycin-dependent mutants of protein S12 are found in this protein, some but not all of which decrease translational accuracy (ram, ribosomal ambiguity mutations). Located at the back of the 30S subunit body where it stabilizes the conformation of the head with respect to the body. The physical location of this protein suggests it may also play a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp. Part of the 30S ribosomal subunit (PubMed:363452, PubMed:4273819, PubMed:12809609, PubMed:16272117, PubMed:27934701, PubMed:10094780, PubMed:12244297, PubMed:27906160, PubMed:27906161, PubMed:28077875). Contacts proteins S4 and S8. With proteins S4 and S5 encircles the mRNA as it enters the ribosome, which may play a role in mRNA helicase processivity (PubMed:15652481). Can be cross-linked to mRNA (PubMed:1712292). The N-terminal domain interacts with the head of the 30S subunit; the C-terminal domain interacts with the body and contacts protein S4. The interaction surface between S4 and S5 is involved in control of translational fidelity. Altered S5 proteins have been identified in a number of mutants. Some mutations in S5 have been shown to increase translational error frequencies. Some mutants in this protein can partially suppress an alanyl-tRNA synthetase mutant. Belongs to the universal ribosomal protein uS5 family.