Host factor for coliphage Q beta RNA replication: presence in procaryotes and association with the 30S ribosomal subunit in Escherichia coli.

The Host Factor required for in vitro coliphage Q beta RNA replication, a heat-stable RNA binding protein present in uninfected Escherichia coli, has been detected by both immunological and functional tests in Acinetobacter calcoaceticus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Pseudomonas putida. It was not detectable by these criteria in Bacillus stearothermophilus, Bacillus subtilis, Caulobacter crescentus, Micrococcus lysodeikticus, Rhodopseudomonas capsulata or Saccharomyces cerevisiae. In Escherichia coli the Host Factor protein has been shown to be associated with ribosomes. It is demonstrated here that this association is specific for the 30S ribosomal subunit.