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J. Bacteriol., Apr 1997, 2551-2556, Vol 179, No. 8
PA Ryan, JD Macmillan and BA Zilinskas
Hemolysin BL, which is composed of a binding component, B, and two lytic
components, L1 and L2, is the enterotoxin responsible for the diarrheal
food poisoning syndrome caused by strains of Bacillus cereus. To further
characterize the toxin, we sought to clone and sequence the genes encoding
the L1 and L2 proteins. A genomic library was screened with polyclonal
antibody to the L1 and L2 proteins to identify recombinant clones
containing the genes. Five clones reacted with the antibody to L2, but none
reacted with the antibody to L1. Southern hybridization analysis with
oligonucleotide probes designed from the N- terminal amino acid sequences
of the L1 and L2 proteins, in conjunction with immunoblot and nucleotide
sequence analysis, revealed that the recombinant plasmid from one of the
clones contained two genes, hblC and hblD, which encode L2 and L1,
respectively. The two genes are arranged in tandem and are separated by
only 37 bases. The gene which encodes the B component of hemolysin BL
(hblA) is located immediately downstream from the gene encoding the L1
protein. Northern blot analysis of B. cereus RNA showed a 5.5-kb transcript
which hybridized with DNA fragments internal to, or including a portion of,
the coding sequences of the B, L1, and L2 genes, suggesting that the
clustered genes which encode the components of hemolysin BL are
cotranscribed and constitute an operon.
Copyright © 1997, American Society for Microbiology
Molecular cloning and characterization of the genes encoding the L1 and L2 components of hemolysin BL from Bacillus cereus
Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231, USA.
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