Mutational analysis of the tra locus of the broad-host-range Streptomyces plasmid pIJ101.
The tra gene of Streptomyces lividans plasmid pIJ101 encodes a 621-amino-acid protein that can mediate both plasmid transfer and the interbacterial transfer of chromosomal genes (i.e., chromosome-mobilizing ability [Cma]) during mating. Here we report the results of in-frame insertional mutagenesis studies aimed at defining regions of Tra required for these functions. While hexameric linker insertions throughout the tra gene affected plasmid and chromosomal gene transfer, insertions in a 200-amino-acid region of the Tra protein that contains presumed nucleotide-binding motifs and that is widely conserved among a functionally diverse family of bacterial and plasmid proteins (K. J. Begg, S. J. Dewar, and W. D. Donachie, J. Bacteriol. 177:6211-6222, 1995) had especially prominent effects on both functions. Insertions near the N terminus of Tra reduced Cma for either circular or linear host chromosomes to a much greater extent than pIJ101 plasmid transfer. Our results suggest that Cma involves Tra functions incremental to those needed for plasmid DNA transfer.
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA. gpettis@unixl.sncc.lsu.edu
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000235:genetics; D004252:DNA Mutational Analysis; D018014:Gene Transfer Techniques; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013302:Streptomyces / Q000235:genetics*
D001426:Bacterial Proteins; D011994:Recombinant Proteins; C085510:transfer region protein, Staphylococcus