Aggregation of Lysine-Containing Zeins into Protein Bodies in
            <i>Xenopus</i>
            Oocytes

Wallace, John C.; Galili, Gad; Kawata, Evelynn E.; Cuellar, Richard E.; Shotwell, Mark A.; Larkins, Brian A.

doi:10.1126/science.2834822

Cited by 90 publications

(42 citation statements)

References 13 publications

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“…The proteases were incubated in the presence or absence of Triton X-100, which removes the RER membrane surrounding the protein body (22). In the absence of detergent, the 27-kD y-zein was not detected after a 4-h incubation, but the a-zeins remained relatively stable throughout the 24-h period (Fig.…”

Section: Resultsmentioning

confidence: 99%

Purification and Characterization of Zein-Degrading Proteases from Endosperm of Germinating Maize Seeds

Barros¹,

Larkins²

1990

Plant Physiol.

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We have purified a group of four proteases (molecular mass 26-33 kilodalton) from germinating seeds of maize (Zea mays L. var W64A) using ammonium sulfate and isoelectric precipitations, anion exchange chromatography, and electroelution from preparative nondenaturing polyacrylamide gels. Their appearance in the endosperm of germinating seeds coincides with the onset of zein degradation. We have shown that these proteases degrade zeins dissolved in alcoholic solution as well as aggregated in protein bodies from developing maize kernels. The apparent molecular weights and net negative charges of each of these proteases are very similar. Additionally, they are inhibited by thiol-blocking agents and activated by reducing compounds. These characteristics suggest that they are a group of cysteine proteases involved in the first steps of storage protein degradation.Storage proteins provide nitrogen, sulfur, and carbon skeletons for the developing embryo during seed germination. Degradation of these proteins in germinating seeds appears to follow a common pattern in many plant species (20). Hydrolysis of the proteins is initiated by the action of cysteine proteinases that cleave internal peptide bonds without causing extensive modifications. The first cysteine proteinase to act, designated proteinase A, is synthesized de novo. The limited hydrolysis by proteinase A generates sites for the action of proteinase B, another type of cysteine proteinase, which is inactive against the native substrate. The carboxyl-ends exposed by the concerted action of proteinases A and B are attacked by carboxypeptidases, and these are normally serine proteases. Finally, tri-and dipeptides are degraded into amino acids by the action of amino-and dipeptidases.Evidence in support of this model comes from angiosperm as well as gymnosperm species (20). Vetch ( Vicia sativa L.) was one of the first species in which the components of this model were identified, isolated, and characterized (19). In mung bean (Vigna radiata L.), the proteolytic enzymes in germinating seeds were also extensively characterized (4), and most of the components of this model are recognized. In cereals, the pathway of storage protein degradation is not as well defined as in dicotyledons. However, the participation of proteinase A followed by the action of carboxypeptidases has been observed in several cereal species (20). 297In maize (Zea mays L.), the storage proteins comprise a group of alcohol-soluble polypeptides called zeins (6). Zeins accumulate in the endosperm during seed development and make up about 50% of total endosperm proteins in mature seeds. They can be divided into subclasses based on solubility and apparent molecular weights: a-zeins, molecular masses 19 and 22 kD, are readily soluble in 70% ethanol; y-, molecular masses 16 and 27 kD, (-, molecular mass 14 kD, and 6-zeins, molecular mass 10 kD, require reducing agents to be solubilized in ethanol (13).Zein degradation begins around the second DAG3, and by 8 DAG most of the protein in the endosp...

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Section: Resultsmentioning

confidence: 99%

Purification and Characterization of Zein-Degrading Proteases from Endosperm of Germinating Maize Seeds

Barros¹,

Larkins²

1990

Plant Physiol.

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“…The formation of protein bodies in maize is speculated to be partly related to the intrinsic structure of the prolamins. ␣-Zein expressed in Xenopus oocytes was shown to be assembled into protein body-like structures (22). However, the expression of only ␣-zein resulted in the formation of low-density protein bodies, which suggested that all prolamins are necessary for synthesis of normal protein bodies.…”

Section: Discussionmentioning

confidence: 99%

A highly digestible sorghum mutant cultivar exhibits a unique folded structure of endosperm protein bodies

Oria

Hamaker

Axtell

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

189

184

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The endosperm of a sorghum mutant cultivar, with high in vitro uncooked and cooked protein digestibilities, was examined by transmission electron microscopy and ␣-, ␤-, and ␥-kafirins (storage proteins) were localized within its protein bodies. Transmission electron microscopy micrographs revealed that these protein bodies had a unique microstructure related to high protein digestibility. They were irregular in shape and had numerous invaginations, often reaching to the central area of the protein body. Protein bodies from normal cultivars, such as P721N studied here, with much lower uncooked and cooked digestibilities are spherical and contain no invaginations. Immunocytochemistry results showed that the relative location of ␣-and ␤-kafirins within the protein bodies of the highly digestible genotype were similar to the normal cultivar, P721N. ␥-Kafirin, however, was concentrated in darkstaining regions at the base of the folds instead of at the protein body periphery, as is typical of normal cultivars. The resulting easy accessibility of digestive enzymes to ␣-kafirin, the major storage protein, in addition to the increased surface area of the protein bodies of the highly digestible cultivar appear to account for its high in vitro protein digestibility.

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“…However, a-zein can form protein bodies by itself in frog oocytes (Wallace et al, 1988). In maize endosperm, protein bodies are first initiated by the B 5 1000 Figure 9.…”

Section: Discussionmentioning

confidence: 99%

Coexpression of the maize delta-zein and beta-zein genes results in stable accumulation of delta-zein in endoplasmic reticulum-derived protein bodies formed by beta-zein.

et al. 1997

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Zeins, the major seed storage proteins of maize, are of four distinct types: (Y, p, S, and y. They are synthesized on the rough endoplasmic reticulum (ER) in a sequential manner and deposited in ER-derived protein bodies. We investigated the potential for producing sulfur-rich p-zein and 6-zein proteins in leaf and seed tissues by expressing the corresponding genes in a constitutive manner in transgenic tobacco. The 6-zein and @-zein, when synthesized individually, were stable in the vegetative tissues and were deposited in unique, zein-specific ER-derived protein bodies. Coexpression of 6-zein and p-zein genes, however, showed that 6-zein was colocalized in p-zein-containing protein bodies and that the leve1 of 6-zein was fivefold higher in 6-/@-zein plants than in S-zein plants. We conclude that 6-zein interacts with p-rein and that the interaction has a stabilizing effect on 6-zein.

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Aggregation of Lysine-Containing Zeins into Protein Bodies in Xenopus Oocytes

Cited by 90 publications

References 13 publications

Purification and Characterization of Zein-Degrading Proteases from Endosperm of Germinating Maize Seeds

Purification and Characterization of Zein-Degrading Proteases from Endosperm of Germinating Maize Seeds

A highly digestible sorghum mutant cultivar exhibits a unique folded structure of endosperm protein bodies

Coexpression of the maize delta-zein and beta-zein genes results in stable accumulation of delta-zein in endoplasmic reticulum-derived protein bodies formed by beta-zein.

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