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β-Conglycinin, one of the dominant storage proteins of soybean, is a trimer composed of three subunits, A, A′ and β. All subunits are N-glycosylated and A and A′ contain extension regions in addition to the core regions common to all subunits. Non-glycosylated individual subunits and deletion mutants (A c and A′ c ) lacking the extension regions of A and A′ were expressed in Escherichia coli. All recombinant proteins were purified to near homogeneity and appeared to have the correct conformation, as judged by CD, density-gradient centrifugation and gel-filtration profiles, indicating that the N-linked glycans and extension regions are not essential for the folding and the assembly into trimers of β-conglycinin. Densitygradient centrifugation, gel-filtration and differential scanning calorimetry profiles of the recombinant proteins and the native β-conglycinin indicated that the N-linked glycans and extension regions contribute to the dimension of β-conglycinin but not to the density and the thermal stability. Comparing the solubilities of the individual subunits with those of deletion mutants, only the A and A′ subunits were soluble at lower ionic strength (µ Ͻ 0.25) at around the pH value of the endoplasmic reticulum. This suggests that the extension regions play an important role in the prevention of aggregation in the endoplasmic reticulum in analogy with the N-linked glycans.

Oxidation of low-density lipoprotein (LDL) has been implicated in atherogenesis. Antioxidants that prevent LDL from oxidizing may reduce atherosclerosis. This study investigated LDL antioxidant activity in edible plant products for development of dietary supplementation to prevent atherosclerosis. Fifty-two kinds of edible plants were extracted using 70% aqueous ethanol solution, and the antioxidant activity of the extracts, which inhibit human LDL oxidation induced by copper ion, was determined on the basis of the oxidation lag time and represented as epigallocatechin 3-gallate equivalent. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic content were also measured for comparisons with antioxidant activity in LDL. Plant products showing the greatest activity in LDL oxidation assay were akamegashiwa (Mallotus japonicus) leaf, Japanese privet (Ligustrum japonicum) leaf, green tea [Camellia sinensis (L.) O. Kuntze], and astringent persimmon (Diospyros kaki). The present study revealed high levels of LDL antioxidant activity in plant products for which such activity levels are underestimated in the DPPH radical scavenging assay and Folin-Ciocalteu assay.

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The effects of dietary consumption of mulberry (Morus alba L.) leaves and their major flavonol glycoside, quercetin 3-(6-malonylglucoside) (Q3MG), on the development of atherosclerotic lesions, in relation to the susceptibility of plasma LDL to oxidative modification, was studied in LDL receptor-deficient (LDLR-/-) mice. Male mice aged 8 wk were randomly assigned to 4 groups (control, quercetin, Q3MG, and mulberry). The control group was fed an atherogenic-diet containing 3 g cholesterol and 15 g cocoa butter/100 g. The other experimental groups were fed the same atherogenic diet supplemented with 0.05 g quercetin/100 g for the quercetin group, 0.05 g Q3MG/100 g for the Q3MG group, and 3 g dried mulberry-leaf powder/100 g for the mulberry group. The mice were fed their respective diets for 8 wk. The susceptibility of LDL to oxidative modification was significantly decreased in the Q3MG- and mulberry-treated mice, as evidenced by the 44.3 and 42.2% prolongation of the lag phase for conjugated diene formation compared with that of the control mice. The atherosclerotic lesion area in both the Q3MG- and mulberry-treated mice was significantly reduced by 52% compared with that of the controls. However, in the quercetin group, no protective effects were observed against LDL oxidation or atherosclerotic lesion formation. In conclusion, mulberry leaves attenuated the atherosclerotic lesion development in LDLR-/- mice through enhancement of LDL resistance to oxidative modification, and these antioxidative and antiatherogenic protective effects were attributed mainly to Q3MG, the quantitatively major flavonol glycoside in mulberry leaves.

Saline-soluble glycinins and insoluble glutelins are the major storage proteins in soybean (Glycine max) and rice (Oryza sativa), respectively. In spite of their differences in solubility properties, both proteins are members of the 11S globulin gene family based on their similarities in primary sequences and processing of the coded protein. Wild-type and methionine-modified glycinin coding sequences were expressed in transgenic rice plants under the control of the rice glutelin GluB-1 promoter. Glycinins were specifically synthesized in the endosperm tissue and co-localized with glutelins in type II protein bodies. They assembled into 7S and 11S species, similar to what was observed in developing soybean seeds. This pattern was quite different from that displayed by the rice glutelins in untransformed plants, in which processed subunits sedimenting at 2S were apparent. In glycinin-expressing transgenic plants, however, glutelins were observed sedimenting at 7S and 11S with lesser amounts in the 2S region. A portion of the glycinins was also found associated in the insoluble glutelin fraction. Renaturation experiments suggested that the hybrid glycinin-glutelin oligomers were formed through specific interactions. Overall, these results indicate that despite significant differences in the assembly of soybean glycinin and rice glutelin, both proteins can assemble with each other to form soluble hexameric oligomers or insoluble aggregates.Seed storage proteins were initially classified into albumins (water soluble), globulins (saline soluble), prolamins (alcohol soluble), and glutelins (residue) by Osborne (1924) according to their solubility properties. Based on more recent and extensive molecular and biochemical analysis of the storage protein genes and their coded products, the storage proteins fall into two major groups, the globulins and the prolamins (Shewry and Tatham, 1990). The rice (Oryza sativa) glutelins and soybean (Glycine max) glycinins are excellent examples of this reclassification of storage proteins. The rice glutelins, which comprise up to 70% to 80% of the total seed protein, are insoluble in a neutral saline solution but soluble in a diluted acid/alkaline solution. They exist as large macromolecular complexes formed by disulfide and hydrophobic interactions of acidic and basic polypeptides. The soybean glycinins, which account for 40% of the total proteins (Utsumi, 1992; Utsumi et al., 1997), are soluble in neutral saline solutions. These proteins accumulate as 11S oligomers comprised of six pairs (subunits) of acidic and basic polypeptides interlinked by a conserved disulfide bond. Although glutelin and glycinin have different properties (such as their solubility), they nevertheless are related and are both members of the 11S globulin family of storage proteins. These proteins share 32% to 37% identity in their primary sequences. Moreover, both proteins are synthesized as a larger precursor on the ER, are proteolytically processed into acidic and basic polypeptides, and are accumulated and...

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