The glycosylated seed storage proteins of Glycine max and Phaseolus vulgaris. Structural homologies of genes and proteins.

TLDR

Considerable information is now available concerning the 7 S seed storage proteins of legumes and the genes that encode them. The study compares the beta‑type subunit gene of common bean phaseolin with the alpha′‑subunit gene of soybean beta‑conglycinin and examines conserved 5′‑flanking sequences for potential regulatory roles. The comparison analyzes 2880 bp of Pvu beta and 3636 bp of Gma alpha′, including ~1 kb of 5′‑flanking, untranslated regions, and the six exons and five introns positioned similarly in both genes. Analysis of pea 7 S gene sequences shows that the size difference between soybean Gma alpha′ and smaller bean/pea polypeptides arises from a large insertion in Gma alpha′’s first exon, and that conserved features span exon boundaries while nonconserved regions may allow protein modification.

Abstract

Considerable information is now available concerning the 7 S seed storage proteins of legumes and the genes that encode them. Our study compares the gene encoding a beta-type subunit of phaseolin (Pvu beta), the 7 S protein of common bean (Phaseolus vulgaris), with the gene encoding an alpha'-subunit of beta-conglycinin (Gma alpha'), the 7 S protein of soybean (Glycine max). The comparison involves 2880 base pairs of Pvu beta and 3636 base pairs of Gma alpha' and includes approximately 1 kilobase pair of 5'-flanking sequences, and 5' and 3' untranslated sequences, as well as the six exons and five introns that are found to occur in similar positions in both genes. Conserved sequences in the 5'-flanking regions of these genes are discussed in light of their potential regulatory role. Published sequences for 7 S genes of pea (Pisum sativum) permit the inference of the nature and direction of evolutionary change and, in particular, show that the major size difference between the large Gma alpha' polypeptide and the smaller polypeptides of pea and common bean is due to a large insertion in the first exon of Gma alpha'. Comparisons of protein primary structure, potential glycosylation sites, and predicted protein hydropathy show that strongly conserved features of 7 S proteins cut across exon boundaries and that nonconserved regions exist that may have potential for protein modification.