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

Escribano, J., Rubio, A., Alvarez-Orti, M., Molina, A., Fernandez, J.A.
Journal of agricultural and food chemistry 2000 v.48 no.2 pp. 457-463
mannans, lectins, amino acid sequences, Crocus sativus, corms, molecular weight
Despite the economical interest of Crocus sativus, its biochemistry has been 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 analyses indicated that the native protein forms noncovalently linked aggregates 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. Their N-terminal sequences shared 25% similarity and were homologous to the N- and C-terminal domains of monocotyledonous mannose-binding lectins, respectively. 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. The native lectin specifically interacts with a yeast mannan and is a major corm protein specifically expressed in this organ.