CHARACTERIZATION OF THE YAM TUBER STORAGE PROTEIN DIOSCORIN

Citation
S. Conlan et al., CHARACTERIZATION OF THE YAM TUBER STORAGE PROTEIN DIOSCORIN, Journal of plant physiology, 153(1-2), 1998, pp. 25-31
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0176-1617
Volume
153
Issue
1-2
Year of publication
1998
Pages
25 - 31
Database
ISI
SICI code
0176-1617(1998)153:1-2<25:COTYTS>2.0.ZU;2-X
Abstract
Dioscorin (M-r 31,000) is the major soluble protein present in the tub ers of the tropical root crop yam (Dioscorea spp.) and in view of its abundance is considered to act as a storage protein. Because of the im portance of the tuber as food for human nutrition the characterisation of dioscorin from Dioscorea cayenensis was undertaken to evaluate the possibility of crop improvement through generic modification. Six cha rge isomers were detected by IEE with pIs in the range 5.68-6.38, and 2-D non-reduced/reduced SDS-PAGE showed two major groups of components differing in the presence or absence of intra-chain disulphide bonds. The partial amino acid sequence determined from the protein N-terminu s and a V8 protease cleavage product agreed with the sequences deduced from the nucleotide sequences of cDNAs. Circular dichroism spectrosco py showed a secondary structure rich in alpha-helix which agreed with secondary structure predictions based on the protein sequence. A signi ficant degree of sequence similarity was found between dioscorins and alpha-carbonic anhydrase enzymes from animals. However, dioscorin may not be an active enzyme due to the presence of amino acid substitution s in the region corresponding to the carbonic anhydrase active site. I mmuno-localisation experiments showed that dioscorin accumulates speci fically in the vacuoles of tuber cells, as reported for the tuber stor age proteins of potato and sweet potato.