Cloning and structural analysis of a cDNA clone encoding glycinin (Gly-1) seed storage protein of peanut

Abstract

A cDNA clone (peanut Gly-1) encoding for glycinin protein was isolated from the immature seeds (from yellow-1 maturity pods) and characterized. The clone spanning a total of 1836 bp, predicted protein of 529 amino acid residues with a calculated mass of 60,447.61 Da. Peanut Gly-1 sequence comparison shows high level of sequence homology with other two peanut glycinin (arachin) genes [Ara h3 (95%) and Ara h4 (94%)] and glycinin (legumin) genes of other legumes such as soybean, broad bean, French bean and pea etc., both at nucleotide (67 to 69%) and amino acid (60 to 63%) levels. The N-and C-terminals of peanut Gly-1 are highly conserved with other glycinin genes; central region of the gene possess three variable regions, which also show conservation with other glycinin genes. peanut glycinin-1 gene deciphers 11S type A seed storage protein. Mapping for conserved domains indicate that peanut Gly-1 consists of bi-cupin domain.RNA gel blot studies demonstrate that the gene expressed during embryo development that is transcriptionally activated early in embryogenesis (white pod maturity) and is repressed late in seed maturation (orange pod maturity stage). Peanut Gly-1 does not express in other tissues like leaf, stem, root, flower, pegs or post germinating seedlings.Seed proteins are an extremely and increasingly important component of nutrition for both humans and animals (Shewry and Casey, 1999). Plant proteins are the cheapest available sources of protein in many countries where few can afford meat or dairy products, hence are an important part of human diet. Supply of proteins from plant is considered an ideal source of protein to humans without the concern of cholesterol and legumes have been well documented for their high seed storage protein contents (Shewry and Casey, 1999).Peanut (Arachis hypogaea L.), a legume with 24% protein (Cherry, 1977), is a major source of plant protein in most tropical and subtropical regions of the world. In the United States, peanuts are mostly grown in the southern states and they have significant economic impact. Peanuts are the third most important source of plant protein and provide approximately 11% of the world's protein supply. The globulin fraction of peanut seed consists of arachin (glycinin or legumin) and con-arachin (vicilin or conglycinin) (Johnson et al. 1950;Cherry et al. 1973). Of the globulins, glycinin (arachin) accounts for more than 50% of the total protein (Jones and Horn, 1930). Glycinin is superior to con-glycinin from the viewpoint of nutritional value (Millerd, 1975) as well as functional properties (Kinsella, 1978). Immunological studies also demonstrate that glycinin type seed storage peanut proteins (such as Ara h3 and Ara h4) are less severe compared to their vicilin (Ara h1) and conglutin (Ara h2) type seed storage proteins (Burks et al. 1995;Shin et al. 1998;Viquez et al. 2003;Koppelman et al. 2004). It is obvious, that it is important to understand the biosynthesis, targeting and biological functions of seed proteins as a prerequisite to their rati...

Peanut proteins: Applications, ailments and possible remediation

“…They are basically glycoproteins containing neutral amino sugar moiety, although the sugar content is very low [2]. The major properties of these two proteins are compared in Tables 2 and 3.…”

“…Peanut proteins have been customarily classified as albumins (water soluble) or globulins (saline soluble) [1]. The globulins are made up of two major proteins, arachin and conarachin [2]. Arachin and conarachin find a number of applications in diverse fields, the most important being the food industry.…”

Cysteine-containing peptides are produced by sequential clipping, but not released, from lupin 11S storage globulin during early germination

“…Lupin legumin (Figure 3) shows a conserved cupin metal-binding site located close to one cysteine in the major subunit, in which the second hystidine is substitute by a lysine. Such sequence variation is also present in few other legumin sequences found in peanut, soybean and fababean [16] and could alter the binding features of the site.…”