Characterization of a mannose-binding lectin from channel catfish (Ictalurus punctatus)

Mannose-binding lectin (MBL) is an important component of innate immunity capable of activating the lectin pathway of the complement system. A MBL gene was isolated from channel catfish (Ictalurus punctatus). The deduced protein contains a canonical collagen-like domain, a carbohydrate recognition domain (CRD), and a neck region similar to mammalian mannose-binding lectin. The catfish mannose-binding lectin CRD contains the EPN motif shown previously to mediate mannose specificity. The catfish mannose-binding lectin showed 30-43% identity with MBL protein sequences of rainbow trout, zebrafish, common carp, and goldfish, and 33-35% identity with sequences of mammalian species. In this study, while liver was the predominant source of mannose-binding lectin gene expression in healthy tissues, mannose-binding lectin expression in spleen rose sharply following challenge with a Gram-negative bacterium.