Molecular Characterization of Oat Seed Globulins

Abstract

We have isolated full-length cDNA clones that encode oat (Avena sativa) seed storage globulin mRNAs from a cDNA library in the expression vector lambda gtll. The longest of these clones, pOG2, has an 1840-base pair insert that encodes a complete precursor subunit with a signal peptide of 24 amino acids followed by an acidic polypeptide of 293 amino acids and a basic polypeptide of 201 amino acids. Near the C terminus of the acidic polypeptide are four repeats of a higly conserved, glutamine-rich octapeptide. Other oat globulin cDNA clones contain five of these repeats. Nucleotide sequence comparisons between these clones indicate that the genes encoding these proteins are highly conserved. We estimate there to be 7 to 10 genes for the oat globulin per haploid genome. Comparisons of amino acid sequences show that the oat globulin is 30 to 40% homologous with storage globulins of legumes and about 70% homologous with the rice seed storage globulin (glutelin).During their development, plant seeds accumulate large amounts of storage proteins that serve as sources of nitrogen, sulfur, and carbon compounds during seed germination (25). Two major classes of storage proteins can be distinguished: globulins, which are found principally in the cotyledons and axis of the embryo, and prolamines, which are found in the endosperm of cereal seeds (13). Two major types of storage globulins have been described that have sedimentation coefficients ofabout 7S and 11S. The proportion of the two types of globulins is variable among dicots; monocot embryos contain only the 7S globulin, which is present in the scutellum.Storage globulins account for most of the protein in dicot seeds, but they generally make up only a small fraction of the protein found in cereal seeds. Instead, most cereals contain predominantly prolamine-type storage proteins. Oats and rice are exceptions. These two contain only small amounts ofprolamine (5-10%), and most of their storage protein is an 11 to 12S globulin that is synthesized in the endosperm. Both of these proteins are structurally related to the 11S globulins found in dicots (25), but both are much less soluble than the dicot 11S globulins. The oat globulin requires 0.8 to 1.0 M NaCl for solubility, whereas the characteristics of the rice globulin (glutelin) are such that denaturing solvents are required for solvation.Previous studies in our laboratory (29) and elsewhere (5, 7)

Angiotensin converting enzyme inhibitory peptides in Finnish cereals: a database survey

“…Results presented in this study are based on database surveys that were performed in the protein structure database environment (iProClass), which consists of reported protein structures. Therefore some variation in primary structures of certain proteins may exist within a species; for instance, at least three slightly different primary structures are reported in the database for 12S oat globulins (Shotwell et al 1988(Shotwell et al , 1990Schubert et al 1990;Tanchak et al 1995). Certain structural characteristics were evident.…”

Characterization of the glycinin gene family in soybean.

“…f Gutelin cDNA from Oriza sativa (Takaiwa et al, 1986). g Globulin from Avena sativa (Shotwell et al, 1988).…”

“…Figure 4 shows that the five glycinin genes share a common structure and have coding regions that are interrupted by introns three times. The presence of three introns is conserved in the homologous legumin-like genes of pea (Lycett et al, 1984), rice (Takaiwa et al, 1986(Takaiwa et al, , 1987, and oat (Shotwell et al, 1988). Homologous genes in the bean Vicia faba (LeB4, Baumlein et al, 1986) and sunflower (T. Thomas, personal communication) are the only 11S genes that have been reported so far that do not contain three introns.…”

Ginkgo 11S seed storage protein family mRNA: unusual Asn-Asn linkage as post-translational cleavage site

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15]. To understand the extent of evolutionary distribution throughout spermatophyta and the fundamental organization of the primary structure of this protein family, it is important to study the structures of conserved proteins in phylogenetically diverse groups of plants.…”