A LECTIN AND A LECTIN-RELATED PROTEIN ARE THE 2 MOST PROMINENT PROTEINS IN THE BARK OF YELLOW WOOD (CLADRASTIS-LUTEA)

Using a combination of cDNA cloning and protein purification it is dem onstrated that bark of yellow wood (Cladrastis lutea) contains two man nose/glucose binding lectins and a lectin-related protein which is dev oid of agglutination activity. One of the lectins (CLAI) is the most p rominent bark protein. It is built up of four 32 kDa monomers which ar e post-translationally cleaved into a 15 kDa and a 17 kDa polypeptide. The second lectin (CLAII) is a minor protein, which strongly resemble s CLAI except that its monomers are not cleaved into smaller polypepti des. Molecular cloning of the Cladrastis lectin family revealed also t he occurrence of a lectin-related protein (CLLRP) which is the second most prominent bark protein. Although CLLRP shows sequence homology to the true lectins, it is devoid of carbohydrate binding activity. Mole cular modelling of the three Cladrastis proteins has shown that their three-dimensional structure is strongly related to the three-dimension al models of other legume lectins and, in addition, revealed that the presumed carbohydrate binding site of CLLRP is disrupted by an inserti on of three extra amino acids. Since it is demonstrated for the first time that a lectin and a noncarbohydrate binding lectin-related protei n are the two most prominent proteins in the bark of a tree, the biolo gical meaning of their simultaneous occurrence is discussed.