The role of proteolysis in the processing and assembly of 11S seed globulins
The role of proteolysis in the processing and assembly of 11S seed globulins
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DOI：
10.1105/tpc.10.3.343
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发表时间：
1998-03-01
期刊：
影响因子：
11.6
通讯作者：
Nielsen, NC
中科院分区：
文献类型：
--
作者：
Jung, R;Scott, MP;Nielsen, NC
11S种子贮藏蛋白是作为翻译后在贮藏液泡中被天冬酰胺内肽酶裂解的前体合成的。为了研究该天冬酰胺内肽酶催化反应的特异性，我们制备了一系列八肽和突变型豆素B和G4甘氨酸亚基。它们在切割位点周围的区域含有氨基酸突变。该内肽酶对断肽键n端Asn具有绝对特异性，但对c端氨基酸的特异性较低。在体外组装六聚体需要切割三聚体中的亚基，编码不可切割的前体蛋白亚基（LeB Delta N-281）的突变基因的产物在转基因烟草种子中积累为三聚体，但未修饰的前体蛋白B基因的产物积累为六聚体，因此，六聚体的组装需要天冬酰胺内肽酶。
11S seed storage proteins are synthesized as precursors that are cleaved post-translationally in storage vacuoles by an asparaginyl endopeptidase. To study the specificity of the reaction catalyzed by this asparaginyl endopeptidase, we prepared a series of octapeptides and mutant legumin B and G4 glycinin subunits. These contained amino acid mutations in the region surrounding the cleavage site. The endopeptidase had an absolute specificity for Asn on the N-terminal side of the severed peptide bond but exhibited little specificity for amino acids on the C-terminal side. The ability of unmodified and modified subunits to assemble into hexamers after post-translational modification was evaluated, Cleavage of subunits in trimers is required for hexamer assembly in vitro, Products from a mutant gene encoding a noncleavable prolegumin subunit (LeB Delta N-281) accumulated as trimers in seed of transgenic tobacco, but products from the unmodified prolegumin B gene accumulated as hexamers, Therefore, the asparaginyl endopeptidase is required for hexamer assembly.