title: A novel peptidoglycan recognition protein containing a goose-type lysozyme domain from the Pacific oyster, Crassostrea gigas.
abstract: Peptidoglycan recognition protein (PGRP) is considered an essential molecule for effective immunity in invertebrates by its detection and clarification of invading bacteria. Bivalve mollusks also possess PGRP systems for self-defense, however, their functions in bivalves remain to be understood. In the present study, cDNA of a novel PGRP was identified from the Pacific oyster, Crassostrea gigas, using EST-based RACE PCR. This novel PGRP is homologous to short PGRPs and the presence of a signal peptide was predicted. The PGRP is classified into the short PGRP group, although its molecular weight was estimated as 54 kDa, close to that of long PGRP groups. A conserved domain search detected amidase_2/PGRP and goose-type (g-type) lysozyme domains in this PGRP structure, and thus this novel PGRP was designated as CgPGRP-L. Catalytic residues for PGRP and g-type lysozyme are well conserved, suggesting that CgPGRP-L may have both binding and lytic functions against bacteria. Reverser transcription PCR (RT-PCR) detected CgPGRP-L mRNA expression in circulatory hemocytes, and quantitative real-time RT-PCR revealed that its expression increased after Marinococcus halophilus and Vibrio tubiashii exposure. These results indicate that CgPGRP-L is expressed in hemocytes by bacterial invasion, and then may play roles of a short PGRP and bacterio-lytic lysozyme.
authors.affiliation: Laboratory of Aquaculture Biology, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiya-machi, Aoba-ku, Sendai 981 8555, Japan. nitoh@bios.tohoku.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Itoh
authors.forename: Keisuke G
authors.initials: KG
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D003001:Cloning, Molecular; D049896:Crassostrea / Q000737:chemistry / Q000235:genetics*; D018076:DNA, Complementary / Q000302:isolation & purification; D005777:Geese / Q000235:genetics; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; C118897:peptidoglycan recognition protein; D009113:Muramidase