Cloning, genetic characterization, and nucleotide sequence of the hemA-prfA operon of Salmonella typhimurium.

摘要: The first step in heme biosynthesis is the formation of 5-aminolevulinic acid (ALA). Mutations two genes, hemA and hemL, result auxotrophy for ALA Salmonella typhimurium, but roles played by these genes mechanism synthesis are not understood. I have cloned sequenced S. typhimurium gene. predicted polypeptide sequence HemA protein shows no similarity to known synthases, synthase activity was detected extracts prepared from strains carrying Genetic analysis, DNA sequencing amber mutations, maxicell studies proved that open reading frame identified encodes HemA. Another surprising finding this study lies directly upstream prfA, which peptide chain release factor 1 (RF-1). A hemA::Kan insertion mutation, constructed vitro, transferred chromosome used show form an operon. gene ends with codon, recognized RF-1. suggest a model autogenous control prfA expression translation reinitiation.