cDNAs for canavalin and concanavalin A from Canavalia gladiata seeds. Nucleotide sequence of cDNA for canavalin and RNA blot analysis of canavalin and concanavalin A mRNAs in developing seeds

Abstract

By a method of Escherichia coli expression-vector-primed cDNA synthesis, a cDNA expression library was constructed from total poly(A)-rich RNA that was prepared from immature embryos of Canavalia gladiata. Essentially full-length cDNA clones for two seed proteins, canavalin and concanavalin A, were selected from the library by immunological screening of the colonies and in vitro RNA synthesis and translation. The complete amino acid sequence of canavalin was determined from the nucleotide sequence of the corresponding cDNA and was found to be very homologous to 7S seed proteins of other legumes. The nucleotide sequence of the cDNA predicts a 26-amino-acid extension in the precursor at the amino terminus of the mature canavalin. Canavalin mRNA and concanavalin A mRNA levels at successive stages of the seed development were estimated by RNA blot hybridization and results indicated that the two mRNA levels are differently regulated.