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  • Title: Localization of the lysine epsilon-aminotransferase (lat) and delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase (pcbAB) genes from Streptomyces clavuligerus and production of lysine epsilon-aminotransferase activity in Escherichia coli.
    Author: Tobin MB, Kovacevic S, Madduri K, Hoskins JA, Skatrud PL, Vining LC, Stuttard C, Miller JR.
    Journal: J Bacteriol; 1991 Oct; 173(19):6223-9. PubMed ID: 1917855.
    Abstract:
    Lysine epsilon-aminotransferase (LAT) in the beta-lactam-producing actinomycetes is considered to be the first step in the antibiotic biosynthetic pathway. Cloning of restriction fragments from Streptomyces clavuligerus, a beta-lactam producer, into Streptomyces lividans, a nonproducer that lacks LAT activity, led to the production of LAT in the host. DNA sequencing of restriction fragments containing the putative lat gene revealed a single open reading frame encoding a polypeptide with an approximately Mr 49,000. Expression of this coding sequence in Escherichia coli led to the production of LAT activity. Hence, LAT activity in S. clavuligerus is derived from a single polypeptide. A second open reading frame began immediately downstream from lat. Comparison of this partial sequence with the sequences of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D valine (ACV) synthetases from Penicillium chrysogenum and Cephalosporium acremonium and with nonribosomal peptide synthetases (gramicidin S and tyrocidine synthetases) found similarities among the open reading frames. Since mapping of the putative N and C termini of S. clavuligerus pcbAB suggests that the coding region occupies approximately 12 kbp and codes for a polypeptide related in size to the fungal ACV synthetases, the molecular characterization of the beta-lactam biosynthetic cluster between pcbC and cefE (approximately 25 kbp) is nearly complete.
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