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Structure of bacteriophage SPN 1 S endolysin reveals an unusual two‐module fold for the peptidoglycan lytic and binding activity
Author(s) -
Park Yangshin,
Lim JeongA.,
Kong Minsuk,
Ryu Sangryeol,
Rhee Sangkee
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12555
Subject(s) - lysin , peptidoglycan , biology , bacteriophage , lytic cycle , biochemistry , bacterial outer membrane , bacterial cell structure , cell wall , bacteria , biophysics , escherichia coli , genetics , virus , gene
Summary Bacteriophage SPN 1 S infects the pathogenic G ram‐negative bacterium S almonella typhimurium and expresses endolysin for the release of phage progeny by degrading peptidoglycan of the host cell walls. Bacteriophage SPN 1 S endolysin exhibits high glycosidase activity against peptidoglycans, resulting in antimicrobial activity against a broad range of outer membrane‐permeabilized G ram‐negative bacteria. Here, we report a crystal structure of SPN 1 S endolysin, indicating that unlike most endolysins from Gram‐negative bacteria background, the α‐helical protein consists of two modular domains, a large and a small domain, with a concave groove between them. Comparison with other structurally homologous glycoside hydrolases indicated a possible peptidoglycan binding site in the groove, and the presence of a catalytic dyad in the vicinity of the groove, one residue in a large domain and the other in a junction between the two domains. The catalytic dyad was further validated by antimicrobial activity assay against outer membrane‐permeabilized E scherichia coli . The three‐helix bundle in the small domain containing a novel class of sequence motif exhibited binding affinity against outer membrane‐permeabilized E . coli and was therefore proposed as the peptidoglycan‐binding domain. These structural and functional features suggest that endolysin from a G ram‐negative bacterial background has peptidoglycan‐binding activity and performs glycoside hydrolase activity through the catalytic dyad.