PLANT PHYSIOLOGY , Vol 107, Issue 4 1147-1158, Copyright © 1995 by American Society of Plant Biologists
|
GENE REGULATION AND MOLECULAR GENETICS |
The Major Tuber Storage Protein of Araceae Species Is a Lectin (Characterization and Molecular Cloning of the Lectin from Arum maculatum L.)
EJM. Van Damme, K. Goossens, K. Smeets, F. Van Leuven, P. Verhaert and W. J. Peumans
Laboratory for Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium (E.J.M.V.D., K.G., K.S., W.J.P.)
A new lectin was purified from tubers of Arum maculatum L. by affinity
chromatography on immobilized asialofetuin. Although this lectin is also
retained on mannose-Sepharose 4B, under the appropriate conditions free
mannose is a poor inhibitor of its agglutination activity. Pure
preparations of the Arum lectin apparently yielded a single polypeptide
band of approximately 12 kD upon sodium dodecyl sulfate-polyacrylamide gel
electrophoresis. However, N-terminal sequencing of the purified protein
combined with molecular cloning of the lectin have shown that the lectin is
composed of two different 12-kD lectin subunits that are synthesized on a
single large precursor translated from and mRNA of approximately 1400
nucleotides. Lectins with similar properties were also isolated from the
Araceae species Colocasia esculenta (L.) Schott, Xanthosoma sagittifolium
(L.) Schott, and Dieffenbachia sequina Schott. Sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and gel filtration of the
different Araceae lectins have shown that they are tetrameric proteins
composed of lectin subunits of 12 to 14 kD. Interestingly, these lectins
are the most prominent proteins in the tuber tissue. Evidence is presented
that a previously described major storage protein of Colocasia tubers
corresponds to the lectin.