蛋白质生物合成的第四步:翻译终止后复合物的解体

The Fourth Step of Protein Synthesis: Disassembly of The Posttermination Complex

蛋白质合成过程一般被归纳为由合成的起始、肽链的延伸和合成的终止组成的三步曲.然而,随着对核糖体再循环因子(ribosomerecyclingfactor,RRF)在蛋白质合成过程中作用的深入研究,人们提出了蛋白质生物合成应是四步曲,这第四步就是翻译终止后核糖体复合物的解体,也就是通常说的核糖体循环再利用.简要地介绍了翻译终止后复合物解体的可能机制:核糖体再循环因子和蛋白质合成延伸因子G在核糖体上协同作用催化这一过程的完成.

Protein synthesis is generally known as consisting of three steps: initiation, elongation, and termination. Much less known is the fourth step: disassembly of the posttermination ribosomal complex and recycling of the machinery necessary for the next round of translation. In bacteria, after reaching the end of a protein-coding sequence, the ribosome binds release factor RF-1 or RF-2 in response to stop codon in the ribosomal A site, activating hydrolysis of the polypeptide chain from peptidyl-tRNA. Release factor RF-3 then catalyzes dissociation of RF-1 or RF-2, leaving a posttermination complex consisting of the 70S ribosome, mRNA, and deacylated tRNA in the P site. How the posttermination complex is disassembled for next round of protein synthesis is a very basic process. The possible mechanisms of posttermination complex disassembly during protein synthesis was summarized: the forth step of protein synthesis is catalyzed by the concerted action of ribosome recycling factor (RRF) and elongation factor G (EF-G).