Alteration of the carbohydrate-binding specificity of a C-type lectin CEL-I mutant with an EPN carbohydrate-binding motif

Cel-i is a gal/galnac-specific c-type lectin isolated from the sea cucumber cucumaria echinata. this lectin is composed of two carbohydrate-recognition domains (crds) with the carbohydrate-recognition motif qpd (gln-pro-asp),which is generally known to exist in galactose-specific c-type crds. in the present study,a mutant cel-i with epn (glu-pro-asn) motif,which is thought to be responsible for the carbohydrate-recognition of mannose-specific ctype crds,was produced in escherichia coli,and its effects on the carbohydrate-binding specificity were examined using polyamidoamine dendrimer (pd) conjugated with carbohydrates. although wild-type cel-i effectively formed complexes with n-acetylgalactosamine (galnac)-pd but not with mannose-pd,the mutant cel-i showed relatively weak but definite affinity for mannose-pd. these results indicated that the qpd and epn motifs play a significant role in the carbohydrate-recognition mechanism of cel-i,especially in the discrimination of galactose and mannose. additional mutations in the recombinant cel-i binding site may further increase its specificity for mannose,and should provide insights into designing novel carbohydrate-recognition proteins. © 2013 bentham science publishers.