Lipopolysaccharide and ß-1,3-glucan binding protein in the hard clam (Meretrix meretrix): molecular characterization and expression analysis.

Pattern recognition molecules play an important role in innate immunity by recognizing conserved molecular patterns that are present on the surface of invading microorganisms. In this study, a lipopolysaccharide and ß-1,3-glucan binding protein (LGBP) gene was cloned from the hard clam Meretrix meretrix (designated as Mm-LGBP) by the expressed sequence tags and rapid amplification of cDNA ends method. The cDNA was 1827 bp in length, consisting of a 71-bp 5'-terminal untranslated region, a 62-bp 3'UTR, and a 1734-bp open reading frame encoding a 577-amino acid polypeptide with an estimated molecular mass of 60.7 kDa and a theoretical isoelectric point of 5.56. Characteristic potential polysaccharide binding, cell adhesion, and glucanase motifs were identified in the Mm-LGBP, indicating that Mm-LGBP should be a new member of the LGBP family. Quantitative real-time polymerase chain reaction was developed to detect the mRNA expression level of Mm-LGBP in 6 different tissues. Higher-level mRNA expression of Mm-LGBP was detected in the gill and digestive gland tissues. The upregulation of Mm-LGBP mRNA after Vibrio anguillarum challenge showed that Mm-LGBP play a pivotal role in antibacterial immunity.