Isolation and partial characterisation of four novel plasma lectins from the American lobster Homarus americanus

Although numerous haemolymph-derived crustacean lectins are described, few have been reported for the American lobster Homarus americanus. In the present study, affinity chromatography was used to isolate and partially describe the carbohydrate affinity of four new lectins from H. americanus plasma. HaMBP and HaDNABP were homodimers of ∼30 kDa subunits which bound to mannan- and DNA-agarose columns, respectively. These proteins had partially overlapping elution profiles, and both shared and unique amino acid sequences and fragmentation patterns after trypsin digestion. A third homodimer of ∼29 kDa subunits eluted with HaMBP and HaDNABP under certain conditions. HaNBP occurred as a monomer and dimer of ∼40 kDa subunits and was recovered in relatively large quantities from mannan-agarose with N-acetylated sugars. Transmission electron microscopy revealed HaNBP to be a linear protein composed of multiple globular subunits.