Bacillus cereus is an
opportunistic pathogenic bacterium closely related to
Bacillus anthracis, the causative agent of
anthrax in mammals. A significant portion of the
B. cereus chromosomal genes are common to B.
anthracis, including genes which in B.
anthracis code for putative
virulence and surface proteins.
B. cereus thus provides a convenient
model organism for studying proteins potentially associated with the
pathogenicity of the highly infectious B.
anthracis. The zinc-binding protein of
B. cereus, BcZBP, is encoded from the bc1534 gene which has three homologues to B.
anthracis. The protein exhibits deacetylase activity with the N-acetyl moiety of the
N-acetylglucosamine and the diacetylchitobiose and triacetylchitotriose. However, neither the specific
substrate of the BcZBP nor the
biochemical pathway have been conclusively identified. Here, we present the
crystal structure of BcZBP at 1.8 A resolution. The
N-terminal part of the 234
amino acid protein adopts a
Rossmann fold whereas the
C-terminal part consists of two beta-strands and two alpha-helices. In the
crystal, the protein forms a compact
hexamer, in agreement with
solution data. A
zinc binding site and a potential
active site have been identified in each
monomer. These sites have extensive similarities to those found in two known zinc-dependent
hydrolases with deacetylase activity, MshB and LpxC, despite a low degree of
amino acid sequence identity. The functional implications and a possible
catalytic mechanism are discussed.
