Purification and characterization of a mannan-binding lectin specifically expressed in corms of saffron plant (Crocus sativus L.)

Despite the economical interest of Crocus sativus, its biochemistry has bee n poorly studied. Herein, we have isolated a lectin present in saffron corm by gel-filtration, anion-exchange, and reversed-phase chromatography. One- and two-dimensional PAGE, MALDI-MS, and N-terminal amino acid sequence ana lyses indicated that the native protein forms noncovalently linked aggregat es of about 80 kDa apparent molecular mass, mainly composed of two charged heterogeneous (pI's, 6.69-6.93) basic subunits of approximately 12 kDa. The ir N-terminal sequences shared 25% similarity and were homologous to the N- and C-terminal domains of monocotyledonous mannose-binding lectins, respec tively. An additional polypeptide of around 28 kDa apparent molecular mass was also detected, probably corresponding to a precursor processed into two mature subunits. In addition, the N-terminal domain subunit exhibited 56% similarity with curculin, a sweet protein with taste-modifying activity. Th e native lectin specifically interacts with a yeast mannan and is a major c orm protein specifically expressed in this organ.