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J. Bacteriol., Oct 1995, 5636-5643, Vol 177, No. 19
D Yogev, R Watson-McKown, R Rosengarten, J Im and KS Wise
Variable lipoproteins (Vlp) constitute the major coat protein of Mycoplasma
hyorhinis. They are products of multiple, divergent, single- copy genes
organized in a chromosomal cluster. Three genes, vlpA, vlpB, and vlpC, have
been previously identified in clonal isolates of M. hyorhinis SK76. Each is
linked to a characteristic promoter region containing a homopolymeric tract
of adenine residues [poly(A) tract], subject to hypermutation, that
transcriptionally controls phase variation of vlp genes and leads to
combinatorial surface mosaics of distinct Vlp products. The size of the
natural vlp gene repertoire is unknown but may critically determine the
degree of structural and combinatorial diversity available in this species.
In this study, the vlp repertoire of M. hyorhinis GDL-1 was characterized
and shown to contain three additional genes, vlpD, vlpE, and vlpF,
clustered with other known vlp genes in the order
5'-vlpD-vlpE-vlpF-IS-vlpA-IS-vlpB- vlpC+ ++-3', where IS represents copies
of the IS1221 element of M. hyorhinis. The 5' boundary of this expanded
family was identical to that of the more limited family
5'-vlpA-IS-vlpB-vlpC-3' previously described in a clonal isolate of strain
SK76. A recombinant construct containing vlpD, vlpE, and vlpF expressed
antigenically distinguishable products corresponding to each gene. These
genes encode characteristic C-terminal repetitive regions that are subject
to size variation by insertion or deletion of intragenic repeats but
maintain an extended, charged structure. Each vlp gene also contained
characteristic alternative open reading frames, which provide a potential
reservoir of coding sequence for Vlp diversity, possibly recruited through
insertion and/or deletion mutations.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Increased structural and combinatorial diversity in an extended family of genes encoding Vlp surface proteins of Mycoplasma hyorhinis
Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia 65212, USA.
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