Physicochemical Studies of Conglutin γ, a Storage Globulin From Seeds of Lupinus angustifolius

Abstract

Physicochemical studies are reported for conglutin �, the minor globulin isolated from seeds of L. angustifolius cv. Uniwhite. Isoelectric focusing of the native protein in polyacrylamide gel slabs resolved major and minor broad bands near pH 8.0 and 7.8 respectively. Following reduction of disulfide bonds with β-mercaptoethanol in 8 M urea, the smaller polypeptide chain of known sequence focused near pH 6.9 while the larger chain focused near pH 8.0. Sedimentation equilibrium studies showed that the major component in aqueous buffers at neutral pH is a hexamer of molecular weight 280 000 which dissociates to the monomer of molecular weight 47 000 at pH 4.8. The sequence molecular weight of the small subunit polypeptide is 16 517 [Elleman, T.C. (1977). Aust. J. Biol. Sci. 30, 33-45]. The molecular weights determined for the larger chain by sedimentation equilibrium or column chromatography in 6 M guanidine hydrochloride, and by dodecyl sulfate-polyacrylamide gel electrophoresis, were in the range 28 000-30 000. Optical rotatory dispersion and circular dichroism measurements have been used to establish the approximate proportions of α-helix (15%), β-structure (35%), β-turns (18%) and unordered regions (32%) in the native protein. The denaturation curve for guanidine hydrochloride and the proportions of α-helix (50%), β-turns (18%) and unordered regions (32%) in 80 % trifluoroethanol have been determined.

Heat‐induced synthesis and tunicamycin‐sensitive secretion of the putative storage glycoprotein conglutin γ from mature lupin seeds

“…Therefore, together with the lack of any measurable enzymatic activity [4], no evident physiological role can be attributed to conglutin y so far.…”

“…Conglutin y was partially purified according to Duranti et al [4]. Further purification was accomplished by ionexchange chromatography on CM-cellulose.…”

“…Conglutin y is an oligomeric protein. Each monomer consists of two disulphide-linked subunits of 28-31 kDa and 17 kDa [4,51. The heavy subunit is glycosylated [5].…”

Structure of the cDNA coding for conglutin ?, a sulphur-rich protein from Lupinus angustifolius

“…The differences include the amino acid composition of conglutin 7 [1,6], its subunit structure [2], the physical structure of its aggregates in solution [22] and may also include an ability to bind insulin and insulin-like growth factor [ 14].…”

Isolation and Characterization of Protein Bodies in Lupinus angustifolius

“…The other protein in seeds of lupins, conglutin-y, appears to be an example of a fourth type of storage protein (3). Conglutin-y is a methionine and cysteine-rich protein and has physical and chemical properties quite distinct from the other classes of storage proteins (5,25). Conglutin-y in lupins and the homologous relative in soybeans, "basic 7S globulin" (17) are both present only in relatively small amounts in seeds of the respective species.…”