Affiliation:
1. Department of Biochemistry and Molecular Genetics
2. Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294-2170
Abstract
ABSTRACT
The exosporium of
Bacillus anthracis
spores consists of a basal layer and an external hair-like nap. The nap is composed primarily of the glycoprotein BclA, which contains a collagen-like region with multiple copies of a pentasaccharide side chain. This oligosaccharide possesses an unusual terminal sugar called anthrose, followed by three rhamnose residues and a protein-bound
N
-acetylgalactosamine. Based on the structure of anthrose, we proposed an enzymatic pathway for its biosynthesis. Examination of the
B. anthracis
genome revealed six contiguous genes that could encode the predicted anthrose biosynthetic enzymes. These genes are transcribed in the same direction and appear to form two operons. We introduced mutations into the
B. anthracis
chromosome that either delete the promoter of the putative upstream, four-gene operon or delete selected genes in both putative operons. Spores produced by strains carrying mutations in the upstream operon completely lacked or contained much less anthrose, indicating that this operon is required for anthrose biosynthesis. In contrast, inactivation of the downstream, two-gene operon did not alter anthrose content. Additional experiments confirmed the organization of the anthrose operon and indicated that it is transcribed from a σ
E
-specific promoter. Finally, we demonstrated that anthrose biosynthesis is not restricted to
B. anthracis
as previously suggested.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
40 articles.
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