doi:10.1016/j.bbrc.2007.09.002
Copyright © 2007 Elsevier Inc. All rights reserved.
Identification of the amino acid residues critical for specific binding of the bacteriolytic enzyme of γ-phage, PlyG, to Bacillus anthracis
Hitomi Kikkawaa, Yoshihito Fujinamib, c, Shin-ichi Suzukia and Jiro Yasudab, c,
, 
aThird Department of Forensic Science, National Research Institute of Police Science, Kashiwa 277-0882, Japan
bFirst Department of Forensic Science, National Research Institute of Police Science, 6-3-1 Kashiwanoha, Kashiwa 277-0882, Japan
cCREST, Japan Science and Technology Agency, Saitama 332-0012, Japan
Received 27 August 2007.
Available online 11 September 2007.
References and further reading may be available for this article. To view references and further reading you must
purchase this article.
Abstract
Bacillus anthracis causes anthrax, a lethal disease affecting humans, which has attracted attention due to its bioterrorism potential. γ-Phage specifically infects B. anthracis, and is used for its detection. γ-Phage lysin, PlyG, specifically lyses B. anthracis. Mutational analysis of PlyGB (PlyG binding domain; residues 156–233) indicated that positions 190–199 are necessary for binding to B. anthracis. This region is the central part of PlyGB and is predicted to form a β-sheet. The amino acid residues of this region are also conserved in other lysins specific for B. anthracis. Alanine substitution at position 190 or 199 within this region resulted in significantly reduced binding, suggesting that L190 and Q199 play key roles in binding of PlyGB to B. anthracis. Our observations provide new insight into the mechanism of specific binding of lysin to B. anthracis, and may be useful in establishing new methods for detection of B. anthracis.
Keywords: Bacillus anthracis; γ-phage; PlyG; Binding domain; Mutational analysis; N-Acetylmuramoyl-l-alanine amidase
Fig. 1. Binding activities of PlyGB deletion mutants. (A) Predicted secondary structure of PlyGB. H and E indicate α-helix and β-sheet, respectively. The numbers of amino acid residues in PlyG are shown at the top and the region names are shown below. (B) Schematic representation of the PlyGB deletion mutants. The region names are shown at the top. (C) PlyGB and its deletion mutants purified from E. coli. (D) Binding activities of wild-type PlyGB and its mutants. Binding activity was examined by dot blot assay as described in Materials and methods.
Fig. 2. Binding activities of site-directed mutants of PlyGB. (A) Sequence alignment of region 3N of PlyG and the homologous regions of other amidases. Sequence alignment and analysis were done by GENETYX ver.7 (GENETYX). (B) Site-directed point mutants of PlyGB purified from E. coli. (C) Binding activities of site-directed point mutants examined by dot blot analysis. (D) Binding activities of site-directed mutants analyzed by ELISA. (E) Hydrophobicity of each residue of PlyG. Red diamonds indicate the positions of L190 and Q199. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)