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Journal of Bacteriology, December 2000, p. 6791-6797, Vol. 182, No. 23
Department of Molecular Biology and
Biochemistry, Wesleyan University, Middletown, Connecticut
06459,1 and Division of Biological
Sciences, The University of Montana, Missoula, Montana
598122
Received 7 August 2000/Accepted 21 September 2000
The conserved cp32 plasmid family of Borrelia
burgdorferi was recently shown to be packaged into a
bacteriophage particle (C. H. Eggers and D. S. Samuels, J. Bacteriol. 181:7308-7313, 1999). This plasmid encodes BlyA, a 7.4-kDa
membrane-interactive protein, and BlyB, an accessory protein, which
were previously proposed to comprise a hemolysis system. Our genetic
and biochemical evidence suggests that this hypothesis is incorrect and
that BlyA and BlyB function instead as a prophage-encoded holin or
holin-like system for this newly described bacteriophage. An
Escherichia coli mutant containing the blyAB
locus that was defective for the normally cryptic host hemolysin SheA
was found to be nonhemolytic, suggesting that induction of
sheA by blyAB expression was responsible for
the hemolytic activity observed previously. Analysis of the structural
features of BlyA indicated greater structural similarity to
bacteriophage-encoded holins than to hemolysins. Consistent with holin
characteristics, subcellular localization studies with E. coli and B. burgdorferi indicated that BlyA is solely
membrane associated and that BlyB is a soluble protein. Furthermore,
BlyA exhibited a holin-like function by promoting the
endolysin-dependent lysis of an induced lambda lysogen that was
defective in the holin gene. Finally, induction of the cp32 prophage in
B. burgdorferi dramatically stimulated blyAB
expression. Our results provide the first evidence of a
prophage-encoded holin within Borrelia.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of Borrelia burgdorferi
BlyA and BlyB Proteins: a Prophage-Encoded Holin-Like System


*
Corresponding author. Mailing address: Department of
Molecular Biology and Biochemistry, Wesleyan University,
Middletown, CT 06459-0175. Phone: (860) 685-3556. Fax:
(860) 685-2141. E-mail: doliver{at}wesleyan.edu.
Present address: Pfizer, Discovery Technology Center, Cambridge, MA 02139.
Present address: Center for Microbial Pathogenesis, University of
Connecticut Health Center, Farmington, CT 06030.
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