A new LDLa domain-containing C-type lectin with bacterial agglutinating and binding activity in amphioxus.

Over 1200 C-type lectin gene models have been identified in amphioxus, but only a few of them have been functionally characterized. In this study, we identified a C-type lectin, BjCTL, with domain structure of LDLa-CTLD-EGF_Lam, the first such data in chordates. It was expressed mainly in the notochord and ovary in a tissue-dependent fashion. Recombinant BjCTL was characterized as a typical Ca(2+)-dependent carbohydrate-binding protein capable of agglutinating and binding to both Gram-negative and positive bacteria we tested. In addition, it specifically bound to insoluble lipopolysaccharide, lipoteichoic acid and peptidoglycan, which can be inhibited by galactose. We also showed that the interaction of BjCTL with the bacteria is primarily attributable to CTLD domain. Thus, BjCTL is a novel pattern recognition protein involved in lectin-mediated innate immunity.