Although this protein associates with the 30S subunit of the ribosome it is not considered to be a bona fide ribosomal protein. Associates exclusively with the 30S subunit; there is 0.1 copy per ribosome in the exponential phase and 0.4 copies per ribosome in the stationary phase. This is also true for several other K12 derivatives and strain B/R. Enriched in the periphery of the cell, excluded from the nucleoid (PubMed:21903814). Induced upon entry into stationary phase, this is controlled at least in part by the RpoS sigma factor. Not essential, a quadruple raiA-hpf-rmf-sra knockout strain is significantly outcompeted by wild-type after 4 days growth (PubMed:17277072). Belongs to the SRA family. Was originally thought to be a ribosomal protein.