Rapiejko P J, Gilmore R
Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester 01655-0103, USA.
Cell. 1997 May 30;89(5):703-13. doi: 10.1016/s0092-8674(00)80253-6.
The SRP54 and SR alpha subunits of the signal recognition particle (SRP) and the SRP receptor (SR) undergo a tightly coupled GTPase cycle that mediates the signal sequence-dependent attachment of ribosomes to the Sec61 complex. Here, we show that SRP54 and SR alpha are in the empty site conformation prior to contact between the SRP-ribosome complex and the membrane-bound SR. Cooperative binding of GTP to SRP54 and SR alpha stabilizes the SRP-SR complex and initiates signal sequence transfer from SRP54 to Sec61 alpha. The GTP-bound conformations of SR alpha and SRP54 perform distinct roles, with SR alpha performing a predominant role in complex stabilization. Hydrolysis by both SRP54 and SR alpha is a prerequisite for dissociation of the SRP-SR complex.
信号识别颗粒（SRP）的SRP54和SRα亚基以及SRP受体（SR）经历紧密偶联的GTP酶循环，该循环介导核糖体与Sec61复合体的信号序列依赖性附着。在此，我们表明，在SRP-核糖体复合体与膜结合的SR接触之前，SRP54和SRα处于空位点构象。GTP与SRP54和SRα的协同结合稳定了SRP-SR复合体，并启动了信号序列从SRP54向Sec61α的转移。SRα和SRP54的GTP结合构象发挥不同作用，其中SRα在复合体稳定中起主要作用。SRP54和SRα的水解是SRP-SR复合体解离的先决条件。
