Mannose-binding plant lectins: Different structural scaffolds for a commonsugar-recognition process

Mannose-specific lectins are widely distributed in higher plants and are be lieved to play a role in recognition of high-mannose type glycans of foreig n micro-organisms or plant predators. Structural studies have demonstrated that the mannose-binding specificity of lectins is mediated by distinct str uctural scaffolds, The mannose/glucose-specific legume (e.g., Con A, pea le ctin) exhibit the canonical twelve-stranded beta -sandwich structure. In co ntrast to legume lectins that interact with both mannose and glucose, the m onocot mannose-binding lectins (e.g., the Galanthus nivalis agglutinin or G NA from bulbs) react exclusively with mannose and mannose-containing N-glyc ans. These lectins possess a beta -prism structure. More recently, an incre asing number of mannose-specific lectins structurally related to jacalin (e .g., the lectins from the Jerusalem artichoke, banana or rice), which also exhibit a beta -prism organization, were characterized. Jacalin itself was re-defined as a polyspecific lectin which, in addition to galactose, also i nteracts with mannose and mannose-containing glycans. Finally the B-chain o f the type II RIP of iris, which has the same beta -prism structure as all other members of the ricin-B family, interacts specifically with mannose an d galactose. This structural diversity associated with the specific recogni tion of high-mannose type glycans highlights the importance of mannose-spec ific lectins as recognition molecules in higher plants. (C) 2001 Societe fr ancaise de biochimie et biologie moleculaire / Editions scientifiques et me dicales Elsevier SAS. All rights reserved.