Shutov A D, Bäumlein H, Blattner F R, Müntz K
Laboratory of Protein Chemistry, State University of Moldova, Mateevici str. 60 MD-2009 Kishinev, Republic of Moldova.
J Exp Bot. 2003 Jul;54(388):1645-54. doi: 10.1093/jxb/erg165. Epub 2003 May 13.
When seeds germinate nearly all the proteins are degraded in senescing storage tissue cells. All these proteins act as amino acid reserves which are mobilized to nourish the seedling. Nevertheless, the major amount of the seeds' protein reserve consists of a few enzymatically inactive, abundant, genuine storage proteins. In their metabolism the conflicting processes of biosynthesis, protein turnover and breakdown, are temporally separated. No degradation of correctly formed storage proteins was observed at the time of synthesis and accumulation during seed maturation. Breakdown takes place after a (long) period of rest when seeds germinate and seedlings start growing. At that time genuine storage proteins are no longer synthesized. Genuine storage proteins have evolved structural features permitting controlled temporal patterns of protection and proteolysis. The acquisition of inserted sequence stretches as sites accessible to limited proteolysis played a key role in the evolution of this control system and happened in coevolution of genuine storage proteins with specific proteinases. This can be deduced from the results of current research on the mechanisms of limited and unlimited proteolysis of storage globulins and on storage globulin evolution. The evolved system of controlled structure-function interplay between storage globulins and proteinases is part of a syndrome that, in addition, comprises differential compartmentation and gene expression of storage proteins and proteinases for controlling the total spatial and temporal patterns of globulin storage and mobilization in maturing and germinating seeds.
种子萌发时，衰老的贮藏组织细胞中几乎所有蛋白质都会被降解。所有这些蛋白质都作为氨基酸储备，被动员起来滋养幼苗。然而，种子的主要蛋白质储备由少数几种无酶活性、含量丰富的真正贮藏蛋白组成。在其代谢过程中，生物合成、蛋白质周转和分解等相互矛盾的过程在时间上是分开的。在种子成熟过程中的合成和积累阶段，未观察到正确形成的贮藏蛋白被降解。当种子萌发且幼苗开始生长，经过一段（较长的）休眠期后，分解才会发生。此时不再合成真正的贮藏蛋白。真正的贮藏蛋白已经进化出结构特征，允许控制保护和蛋白水解的时间模式。获得可被有限蛋白水解作用的插入序列片段在这个控制系统的进化中起了关键作用，并且发生在真正的贮藏蛋白与特定蛋白酶的共同进化过程中。这可以从目前关于贮藏球蛋白有限和无限蛋白水解机制以及贮藏球蛋白进化的研究结果中推断出来。贮藏球蛋白和蛋白酶之间进化出的结构 - 功能相互作用控制系统是一个综合征的一部分，此外，该综合征还包括贮藏蛋白和蛋白酶的差异区室化和基因表达，用于控制成熟和萌发种子中球蛋白贮藏和动员的总体时空模式。
