Surface diversity in Mycoplasma agalactiae is driven by site-specific DNA inversions within the vpma multigene locus.
The ruminant pathogen Mycoplasma agalactiae possesses a family of abundantly expressed variable surface lipoproteins called Vpmas. Phenotypic switches between Vpma members have previously been correlated with DNA rearrangements within a locus of vpma genes and are proposed to play an important role in disease pathogenesis. In this study, six vpma genes were characterized in the M. agalactiae type strain PG2. All vpma genes clustered within an 8-kb region and shared highly conserved 5' untranslated regions, lipoprotein signal sequences, and short N-terminal sequences. Analyses of the vpma loci from consecutive clonal isolates showed that vpma DNA rearrangements were site specific and that cleavage and strand exchange occurred within a minimal region of 21 bp located within the 5' untranslated region of all vpma genes. This process controlled expression of vpma genes by effectively linking the open reading frame (ORF) of a silent gene to a unique active promoter sequence within the locus. An ORF (xer1) immediately adjacent to one end of the vpma locus did not undergo rearrangement and had significant homology to a distinct subset of genes belonging to the lambda integrase family of site-specific xer recombinases. It is proposed that xer1 codes for a site-specific recombinase that is not involved in chromosome dimer resolution but rather is responsible for the observed vpma-specific recombination in M. agalactiae.
Glew
Michelle D
MD
Institute of Bacteriology, Mycology and Hygiene, University of Veterinary Medicine, 1210 Vienna, Austria.
Marenda
Marc
M
Rosengarten
Renate
R
Citti
Christine
C
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D007446:Chromosome Inversion; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004269:DNA, Bacterial; D015964:Gene Expression Regulation, Bacterial; D008074:Lipoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D009174:Mycoplasma / Q000235:genetics*; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D012357:RNA, Transfer, Lys; D045522:Recombinases; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008074:Lipoproteins; D008565:Membrane Proteins; D012357:RNA, Transfer, Lys; D045522:Recombinases; D004254:DNA Nucleotidyltransferases