Analysis of Lectin Expression by Immunoblotting

Abstract

Two types of soluble galactoside-binding lectins of 14.5 and 29–35 kDa, respectively, have been studied in different laboratories and found to be distributed widely in species ranging from electric eel to man. Within each species, these lectins exhibit distinct tissue distribution and their levels are regulated during development. The lower and higher molecular weight lectins have been cloned and sequenced and found to share some sequence homology. Their physiological function(s) is not known; however, their ability to bind galactosides and the changes in their level during embryogenesis and development, processes which are also accompanied by changes in glycoconjugates, suggest that the lectins play a role in recognition and cellular interactions (reviewed by Barondes 1988; Lotan 1992). Galactoside-specific lectins have been purified from various tissues by affinity chromatography using different immobilized galactosides or galactoglycoproteins (e.g. asialofetuin). The molecular weights reported for the lectins purified in different laboratories and from different tissues and species vary from 12–15 kDa for the low molecular weight lectin and 29–35 kDa for the higher molecular weight lectin. These will be designated here as L-14.5 and L-34, respectively. Additional galactoside-binding lectins of 6.5,16,17, 18, 22, 67 and 70 kDa have been detected, but only limited information is available on these lectins. The presence of lactoside-binding lectins in tissues and cells can be screened rapidly by immunoblotting using the procedures described below.