[Show abstract][Hide abstract] ABSTRACT: Pea albumin 2 (PA2:Mr≈26000) is a major component of the albumin fraction derived from aqueous salt extracts of pea seed. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and chromatography on DEAE-Sephacel resolve PA2 into two closely related components (PA2a and PA2b). A cDNA clone coding for one of these components has been sequenced and the deduced amino acid sequence compared with partial, chemically-determined sequences for cyanogen bromide peptides from both PA2 components. Complete amino acid sequences were obtained for the C-terminal peptides. The PA2 molecule of 230 amino acids contains four imperfect repeat sequences each of approximately 57 amino acids in length.The combined sequence data, together with a comparison of PA2-related polypeptides produced in vitro and in vivo, indicate that PA2 is synthesized without a signal sequence and does not undergo significant post-translational modification. Although both forms of PA2 contain Asn-X-Thr consensus sequences, neither form is glycosylated. Accumulation of PA2 contributes approximately 11% of the sulfur-amino acids in pea seeds (cysteine plus methionine equals 2.6 residues percent). Suppression of levels of PA2 polypeptides and their mRNAs in developing seeds of sulfur-deficient plants is less marked than that for legumin, in spite of the lower content of sulfur-amino acids in legumin.
[Show abstract][Hide abstract] ABSTRACT: Recent studies in a number of laboratories have characterised many of the properties of a major pea albumin (designated PMA or PA2: subunit Mr∼26 000) which is not readily degraded in the cotyledon upon germination. In the present report, some of the physicochemical properties of this protein have been studied in greater detail. A non-helical structure, stable at high pH, is evident. Of special significance is the presence of a single free sulphydryl group, although studies reported elsewhere show that the protein consists of four copies of a strongly conserved repeated sequence. It is postulated that this free sulphydryl group in PA2 (5–10% of total pea seed protein) causes polymerisation through disulphide interchange and thereby is a likely source of partial insolubility in protein isolates following an initial alkaline extraction.
Journal of the Science of Food and Agriculture 01/1987; 41(2):167 - 178. DOI:10.1002/jsfa.2740410210 · 1.71 Impact Factor