SYNTHESIS AND DEPOSITION OF ZEIN IN PROTEIN BODIES OF MAIZE ENDOSPERM
SYNTHESIS AND DEPOSITION OF ZEIN IN PROTEIN BODIES OF MAIZE ENDOSPERM
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DOI：
10.1104/pp.62.2.256
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发表时间：
1978-01-01
期刊：
影响因子：
7.4
通讯作者：
HURKMAN, WJ
中科院分区：
文献类型：
--
作者：
LARKINS, BA;HURKMAN, WJ
玉米蛋白体的起源研究胚乳以确定它们是否形成为高度分化的细胞器或粗面内质网内的蛋白质沉积物。发育中的玉米胚乳细胞电镜观察表明，蛋白体周围的膜与粗面内质网膜相连。蛋白体和粗面内质网的膜都含有细胞色素c还原酶活性，表明这些膜之间具有相似性。从蛋白体和粗面内质网膜分离的多聚核糖体合成的醇溶性蛋白比例相似，醇溶性蛋白和醇不溶性蛋白显示相同的[14 C]亮氨酸标记。显然，蛋白体只是作为粗面内质网内的沉积物形成的。通过蔗糖梯度离心，将仅指导较小MW玉米醇溶蛋白亚基合成的mRNA与合成两种亚基的mRNA分离。这一结果表明，分离但大小相似的mRNA合成主要的玉米醇溶蛋白组分。纯化的mRNA或多聚核糖体的体外翻译产物比天然玉米醇溶蛋白大约2000道尔顿，表明蛋白质是作为玉米醇溶蛋白前体合成的。当完整的粗面内质网被放置在体外蛋白质合成系统中时，获得分子量与天然玉米醇溶蛋白相对应的蛋白质。
The origin of protein bodies in maize (Zea mays L.) endosperm was investigated to determine whether they are formed as highly differentiated organelles or as protein deposits within the rough endoplasmic reticulum. EM of developing maize endosperm cells showed that membranes surrounding protein bodies were continuous with rough endoplasmic reticulum membranes. Membranes of protein bodies and rough endoplasmic reticulum both contained cytochrome c reductase activity indicating a similarity between these membranes. The proportion of alcohol-soluble protein synthesized by polyribosomes isolated from protein body or rough endoplasmic reticulum membranes was similar and the alcohol-soluble or -insoluble proteins showed indentical [14C]leucine labeling. Apparently protein bodies form simply as deposits within the rough endoplasmic reticulum. mRNA that directed synthesis of only the smaller MW zein subunit was separated from mRNA that synthesized both subunits by sucrose gradient centrifugation. This result demonstrated that separate but similar sized mRNA synthesize the major zein components. In vitro translation products of purified mRNA or polyribosomes were approximately 2000 daltons larger than native zein proteins, suggesting that the proteins are synthesized as zein precursors. When intact rough endoplasmic reticulum was placed in the in vitro protein synthesis system, proteins corresponding in molecular weight to the native zein proteins were obtained.