Immunochemical characterisation of a methionine-rich protein from peanut

Abstract

Peanuts (Arachis hypogeae L. cv. Florunner), like other legumes, are low in sulfur-containing amino acids such as methionine and cysteine. Previous research from our laboratory has resulted in the identification and isolation of a methionine-rich protein (MRP) from peanut. To determine the differential deposition pattern of MRP during seed development and its breakdown pattern during seed germination, immunological studies were conducted using antibodies raised against MRP. The results showed that MRP-3 was deposited very early (in the ‘white’ maturity stage), while the MRP-5 accumulated at a later (the ‘yellow’ maturity stage) stage of seed development. Germination studies showed that MRP-3 degraded after 8 days of germination, while MRP-5 degraded after 10 days of germination. The MRP-3 antibody detected homologous proteins in several other legumes and cereals such as pea, pigeon pea, chick pea, red lentil, brown lentil, rice and wheat, while the MRP-5 antibody reacted with extracts from pea, chick pea and French bean, thus showing a conservation of the MRP subunits across species.