Physico-chemical Characterization of Hemolymph Hemagglutinin of the Marine Crab G. albolineatus

Abstract

Lectins, multivalent cell-agglutinating proteins, by virtue of their exquisite sugar specificities are useful tools in widespread biomedical applications. The present investigation was carried out to study the physico-chemical characteristics of the hemolymph hemagglutinin of the marine crab Grapsus albolineatus. The specificity of agglutinin to erythrocytes, sugars, glycoproteins, pH, temperature and the effects of divalent cations and calcium chelators was determined. A naturally occurring hemagglutinin with high HA titer of 2048 with rat erythrocytes was identified in the hemolymph of the marine crab G. albolineatus. The HA activity was stable between pH 7 and 9 and showed thermal stability between 0˚ and 40˚C. The hemolymph agglutinin was calcium dependent and HA activity was reduced when exposed to calcium chelators such as EDTA and trisodium citrate. Hemagglutination inhibition assay exhibited the strongest binding specificity towards the sugars GalNAc, GlcNAc and glycoprotein fetuin. The cross-adsorption assay revealed that the hemolymph of the marine crab Grapsus albolineatus possesses single agglutinin.