title: A novel short peptidoglycan recognition protein in amphioxus: identification, expression and bioactivity.
abstract: Peptidoglycan recognition proteins (PGRPs) are widely distributed in invertebrates and vertebrates, and structure-activity relationship of insect and mammalian PGRPs has been well characterized, but functional and structural insights into PGRPs in other species are rather limited. Here we identified a novel short PGRP gene from the amphioxus Branchiostoma japonicum, named pgrp-s, which possesses a domain combination of ChtBD1 domain-PGRP domain, which is unique to all known PGRPs. Amphioxus pgrp-s was predominantly expressed in the hepatic caecum, hind-gut and muscle in a tissue-specific manner. Recombinant PGRP-S, rPGRP-S, and truncated protein with ChtBD1 domain deleted, rP86/250, both showed affinity to Dap-type PGN, Lys-type PGN and chitin. Consistently, they were also able to bind to Escherichia coli, Staphylococcus aureus and Pichia pastoris. Moreover, both rPGRP-S and rP86/250 had amidase enzymatic activity, capable of hydrolyzing Dap-type and Lys-type PGNs. Like vertebrate PGRPs, rPGRP-S was directly microbicidal, capable of killing E. coli, S. aureus and P. pastoris, whereas rP86/250 only inhibited the growth of E. coli and S. aureus, and its anti-P. pastoris activity was significantly reduced. It is clear that neither the binding of amphioxus PGRP-S nor its amidase enzymatic activity depend on the N-terminal ChtBD1 domain, but its antifungal activity does. Collectively, these data suggested that amphioxus PGRP-S may function as a multivalent pattern recognition receptor, capable of recognizing PGN and chitin, a microbicidal agent, capable of killing bacteria such as E. coli and S. aureus and fungus like P. pastoris, and probably a PGN scavenger, capable of hydrolyzing PGN.
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Yao
authors.forename: Zhaohe
authors.initials: Z
authors.lastname: Li
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shicui
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001419:Bacteria / Q000166:cytology / Q000276:immunology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D002816:Chordata, Nonvertebrate / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D003001:Cloning, Molecular; D007113:Immunity, Innate; D017434:Protein Structure, Tertiary
chemical_list: D002352:Carrier Proteins; C118897:peptidoglycan recognition protein; D000581:Amidohydrolases; C019665:amidase