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Dev Comp Immunol. 2013 Dec;41(4):618-30. doi: 10.1016/j.dci.2013.06.010. Epub 2013 Jun 24.

First evidence of protein G-binding protein in the most primitive vertebrate: serum lectin from lamprey (Lampetra japonica).

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  • 1Institute of Marine Genomics and Proteomics, Liaoning Normal University, Dalian 116029, China; School of Life Science, Liaoning Normal University, Dalian 116029, China.

Abstract

The intelectins, a recently identified subgroup of extracellular animal lectins, are glycan-binding receptors that recognize glycan epitopes on foreign pathogens in host systems. Here, we have described NPGBP (novel protein G-binding protein), a novel serum lectin found in the lamprey, Lampetra japonica. RT-PCR yielded a 1005 bp cDNA sequence from the lamprey liver encoding a 334 amino acid secretory protein with homology to mammalian and aquatic organism intelectins. Gene expression analyses showed that the NPGBP gene was expressed in the blood, intestines, kidney, heart, gill, liver, adipose tissue and gonads. NPGBP was isolated by protein G-conjugated agarose immunoprecipitation, and SDS-PAGE analyses showed that NPGBP migrated as a specific band (∼35 and ∼124 kDa under reducing and non-reducing conditions, respectively). These results suggested that NPGBP forms monomers and tetramers. NPGBP gene expression was induced by in vivo bacterial stimulation, and NPGBP showed different agglutination activities against pathogenic Gram-positive bacteria, Gram-negative bacteria and fungi. The induction of NPGBP suggested that it plays an important role in defense against microorganisms in the internal circulation system of the lamprey. When incubated with an unrelated antibody, the specific binding between NPGBP and protein G was competitively inhibited, indicating that NPGBP and the Fc region of Ig bind to the same site on protein G. We thus assume that the tertiary structure of NPGBP is similar to that of the Fc region of Ig. Additionally, NPGBP can effectively promote endothelial cell mitosis. These findings suggest that NPGBP plays a role in the immune defense against microorganisms, and this study represents one of the few examples of the characterization and functional analysis of an aquatic organism intelectin.

Copyright © 2013. Published by Elsevier Ltd.

KEYWORDS:

Agglutination activity; Immune defense; Intelectin; Lamprey; Protein G target

PMID:
23806362
[PubMed - indexed for MEDLINE]
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