title: Structure and lytic activity of a Bacillus anthracis prophage endolysin.
abstract: We report a structural and functional analysis of the lambda prophage Ba02 endolysin (PlyL) encoded by the Bacillus anthracis genome. We show that PlyL comprises two autonomously folded domains, an N-terminal catalytic domain and a C-terminal cell wall-binding domain. We determined the crystal structure of the catalytic domain; its three-dimensional fold is related to that of the cell wall amidase, T7 lysozyme, and contains a conserved zinc coordination site and other components of the catalytic machinery. We demonstrate that PlyL is an N-acetylmuramoyl-L-alanine amidase that cleaves the cell wall of several Bacillus species when applied exogenously. We show, unexpectedly, that the catalytic domain of PlyL cleaves more efficiently than the full-length protein, except in the case of Bacillus cereus, and using GFP-tagged cell wall-binding domain, we detected strong binding of the cell wall-binding domain to B. cereus but not to other species tested. We further show that a related endolysin (Ply21) from the B. cereus phage, TP21, shows a similar pattern of behavior. To explain these data, and the species specificity of PlyL, we propose that the C-terminal domain inhibits the activity of the catalytic domain through intramolecular interactions that are relieved upon binding of the C-terminal domain to the cell wall. Furthermore, our data show that (when applied exogenously) targeting of the enzyme to the cell wall is not a prerequisite of its lytic activity, which is inherently high. These results may have broad implications for the design of endolysins as therapeutic agents.
authors.affiliation: Infectious and Inflammatory Disease Center, The Burnham Institute, La Jolla, California 92037, USA.
authors.forename: Lieh Yoon
authors.initials: LY
authors.lastname: Low
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.forename: Marta
authors.initials: M
authors.lastname: Perego
authors.forename: Andrei
authors.initials: A
authors.lastname: Osterman
authors.forename: Robert C
authors.initials: RC
authors.lastname: Liddington
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D001408:Bacillus anthracis / Q000378:metabolism*; D001426:Bacterial Proteins; D001665:Binding Sites; D020134:Catalytic Domain; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D010450:Endopeptidases / Q000737:chemistry*; D016680:Genome, Bacterial; D008954:Models, Biological; D008958:Models, Molecular; D015233:Models, Statistical; D008969:Molecular Sequence Data; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000737:chemistry; D010457:Peptidoglycan / Q000737:chemistry; D039002:Prophages / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013997:Time Factors; D015032:Zinc / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D010457:Peptidoglycan; D010450:Endopeptidases; C001143:endolysin; D000581:Amidohydrolases; C506058:PlyL protein, Bacillus anthracis; D009238:N-Acetylmuramoyl-L-alanine Amidase; C019665:amidase; D015032:Zinc