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The three globulins of the seeds of L. angustifolius cv. Uniwhite may be satisfactorily resolved in 10 min by electrophoresis on cellulose acetate strips. These globulins, conglutins α, β and γ, vary markedly in their amino acid compositions, with conglutin Ω differing from conglutins α and β and most other legume storage proteins in its relatively high content of cystine and methionine and lower content of arginine and glutamic acid. When examined on sodium dodecyl sulphate-polyacrylamide gels, both in the absence and presence of β-mercaptoethanol, the three globulins were found to differ completely in the type of subunit proteins they contain and in the significance of intrachain disulphide bonding. Conglutin α was found to contain three or four types of non-covalently linked subunits with apparent molecular weights in the range 55 000-80 000, each of which may contain a disulphide-bonded moiety with a molecular weight near 20 000. Conglutin γ was found to contain disulphide-bonded chains of molecular weights 17 000 and 30 000, whereas the four major subunits of conglutin β, whose molecular weights lie in the range 20 000-60 000, were not covalently linked together. The latter globulin does not appear to be homogeneous, for it can be separated by fractional precipitation with ammonium sulphate into a series of fractions which differ markedly in the proportion of subunit types they contain.

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.

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