Classification of Plant Lectins in Families Of Structurally and Evolutionary Related Proteins

Abstract
The majority of plant lectins can be classified in seven families of structurally and lutionary related proteins. Within a given lectin family most but not necessarily all mbers are built up of protomers with a similar primary structure and overall 3-D fold. The rall structure of the native lectins is not only determined by the structure of the protomers depends also on the degree of oligomerization and in some cases on the post-nslational processing of the lectin precursors. In general, lectin families are fairly homogeneous for what concerns the overall cificity of the individuallectins, which illustrates that the 3-D structure of the binding site been conserved during evolution. In the case of the jacalin-related lectins the occurrence a mannose-and galactose-binding subfamily can be explained by the fact that a post-nslational cleavage of the protomers (of the galactose-binding subfamily) yields a slightly red binding site. Unlike the other families, the legume lectins display a wide range of cificites, which is clearly reflected in the occurrence of sugar-binding sites with a erent 3-D structure.