Two Putative Polysaccharide Deacetylases Are Required for Osmotic Stability and Cell Shape Maintenance in Bacillus anthracis *

摘要

Background: BA0330 and BA0331 are the only two lipoproteins among 11 known or putative polysaccharide deacetylases from Bacillus anthracis. Results: Both proteins lack deacetylase activity and are important for cell shape maintenance (BA0331) or high salt stress adaptation of the bacterium (BA0330). Conclusion: BA0330 and BA0331 stabilize the cell wall of B. anthracis . Significance: Understanding the mechanisms by which lipoproteins maintain cell wall integrity. Membrane-anchored lipoproteins have a broad range of functions and play key roles in several cellular processes in Gram-positive bacteria. BA0330 and BA0331 are the only lipoproteins among the 11 known or putative polysaccharide deacetylases of Bacillus anthracis . We found that both lipoproteins exhibit unique characteristics. BA0330 and BA0331 interact with peptidoglycan, and BA0330 is important for the adaptation of the bacterium to grow in the presence of a high concentration of salt, whereas BA0331 contributes to the maintenance of a uniform cell shape. They appear not to alter the peptidoglycan structure and do not contribute to lysozyme resistance. The high resolution x-ray structure of BA0330 revealed a C-terminal domain with the typical fold of a carbohydrate esterase 4 and an N-terminal domain unique for this family, composed of a two-layered (4 + 3) β-sandwich with structural similarity to fibronectin type 3 domains. Our data suggest that BA0330 and BA0331 have a structural role in stabilizing the cell wall of B. anthracis .