Structural properties of legume lectins.

The above data provide immunochemical evidence that lectins isolated from different legume species may be structurally related proteins and are probably homologues. This generalization derives from the great overall similarities in physical, chemical and biological properties of these proteins. More specifically, these proteins appear to be immunologically closely related and possess a high degree of conservation in their primary structures. Acceptance of this generalization implies a common physiological function for these proteins. Hence, in the search for their function, serious consideration must be given to the group as a whole. A number of legume species were shown to be totally devoid of proteins with hemagglutinin activity. Without exception, however, these plants contained cross reacting material which was immunologically closely related to one or more of the classic lectins. These results suggest that independent of whether a legume seed extract can agglutinate red blood cells, it appears to contain a protein physiologically homologous to the well studied legume lectins. Further, these observations suggest that "hemagglutinin activity" may not be a required manifestation of the "normal" in vivo activity of this group of proteins. All legumes appear to contain a specific alpha-galactosidase, but only rarely does this enzyme possess hemagglutinin activity. We suspect the hemagglutinin activity associated with the alpha-galactosidase-hemagglutinin molecule may result from slow hydrolysis of cell surface carbohydrate receptors and may not be important with respect to the general functioning of this class of protein. It is clear that a great many questions about these interesting proteins remain to be answered.(ABSTRACT TRUNCATED AT 250 WORDS)