Mj. Revilleza et al., AN 8 KDA METHIONINE-RICH PROTEIN FROM SOYBEAN (GLYCINE-MAX) COTYLEDON- IDENTIFICATION, PURIFICATION, AND N-TERMINAL SEQUENCE, Journal of agricultural and food chemistry, 44(9), 1996, pp. 2930-2935
The genes encoding methionine-rich proteins (MRP) in seeds are candida
tes for overexpression to enhance the nutritional quality of legume pr
oteins, which are relatively deficient in methionine. Our previous wor
k on soybean seed localized the MRP in the albumin fraction, and the p
resent work further localized them in the low molecular weight fractio
n (LMW) of albumin. Enrichment of the albumin fraction for LMW protein
s by heparin-Sepharose affinity chromatography before resolution on 2D
SDS-PAGE and labeling of methionine-containing proteins with [1-C-14]
iodoacetate resulted in identification of three methionine-rich 8 kDa
proteins with different pi values. The most acidic of the three (2D-1)
was recovered for amino acid analysis and partial protein sequencing.
2D-1 had 8.6% methionine, 11.4% lysine, and high amounts of glutamic
acid and aspartic acid. This work lays the groundwork for cloning of t
he gene encoding 2D-1, its eventual overexpression in soybean seed, an
d elucidation of a possible biological role for 2D-1 and related prote
ins.