Dimerization of TOC receptor GTPases and its implementation for the control of protein import into chloroplasts.
Dimerization of TOC receptor GTPases and its implementation for the control of protein import into chloroplasts.
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DOI：
10.1042/bj20110659
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发表时间：
2011-06-01
期刊：
影响因子：
--
通讯作者：
Jarvis, Paul
中科院分区：
文献类型：
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作者：
Aronsson, Henrik;Jarvis, Paul
前蛋白进入叶绿体是由包膜上的多蛋白易位复合物促进的。TOC（叶绿体外膜转座子）复合体的主要成分是受体蛋白Toc33和Toc159。这两种受体是相关的gtp酶，它们被预测参与同二聚化和/或异二聚化。虽然这种二聚化已被广泛研究，但其在体内的确切功能仍然难以捉摸。在这一期的《生化杂志》上，Oreb等人提出了证据，证明Toc33的同二聚化阻止了核苷酸交换，从而将受体锁定在gdp负载状态，阻止了进一步的活性。通过二聚体的破坏和随后的核苷酸交换，提出了蛋白前到达释放这种锁定。然后，toc33结合的前蛋白能够进入转运机制的下游步骤，GTP水解定义了另一个重要的控制点，并为下一个前蛋白客户端准备受体。这些新的结果讨论了在有关TOC受体二聚化和功能的先前发现的背景下。
Pre-protein import into chloroplasts is facilitated by multiprotein translocon complexes in the envelope membranes. Major components of the TOC (translocon at the outer envelope membrane of chloroplasts) complex are the receptor proteins Toc33 and Toc159. These two receptors are related GTPases, and they are predicted to engage in homodimerization and/or heterodimerization. Although such dimerization has been studied extensively, its exact function in vivo remains elusive. In this issue of the Biochemical Journal, Oreb et al. present evidence that homodimerization of Toc33 prevents nucleotide exchange, thereby locking the receptor in the GDP-loaded state and preventing further activity. Pre-protein arrival is proposed to release this lock, through disruption of the dimer and subsequent nucleotide exchange. The Toc33-bound pre-protein is then able to progress to downstream steps in the translocation mechanism, with GTP hydrolysis defining another important control point as well as preparing the receptor for the next pre-protein client. These new results are discussed in the context of previous findings pertaining to TOC receptor dimerization and function.