細(xì)胞生物學(xué)11核糖體-wenkub
2023-01-31 21:15:03 本頁面
【正文】 ite, forming a peptidyltRNA in the A site and a deacylated tRNA in the P site. The reaction is catalyzed by a part of the 28S rRNA acting as a ribosome. In step 3, the binding of factor G and the hydrolysis of its associated GTP results in the translocation of the ribosome relative to the mRNA. Translocation is acpanied by the movement of the deacylated tRNA and peptidyltRNA into the E and P sites, respectively. In step 4, the deacylated tRNA leaves the ribosome, and a new aminoacyltRNA enters the A site. (b) Peptide bond formation and the subsequent displacement of the deacylated tRNA. 三、 RNA在生命起源中的 地位及其演化過程 ? 生命是自我復(fù)制的體系 ? DNA代替了 RNA的遺傳信息功能 ? 蛋白質(zhì)取代了絕大部分 RNA酶的功能 Evolution of RNAs that can direct Protein synthesis Evolution of new enzymes that create and make RNA copies from it Question Discussing the following: During the evolution of life on the earth, RNA has been demoted from its glorious position as the first selfreplicating catalyst. Its role now is as a mere messenger in the information flow from DNA to protein. 生命是自我復(fù)制的體系 ?三種生物大分子，只有 RNA既具有信息載體功能又具有酶的催化功能。 r 蛋白質(zhì)的主要功能 ?對 rRNA 折疊成有功能的三維結(jié)構(gòu)是十分重要的； ?在蛋白質(zhì)合成中 , 某些 r蛋白可能對核糖體的構(gòu)象起 “ 微調(diào) ” 作用； ?在核糖體的結(jié)合位點(diǎn)上甚至可能在催化作用中 , 核糖體蛋白與 rRNA共同行使功能 。 (a) Important Binding Sites on the Prokaryotic Ribosome This model of ribosome structure shows the A (aminoacyl) and P (peptidyl) sites as cavities on the ribosome where charged (amino acidcarrying) tRNA molecules bind during polypeptide synthesis. The more recently postulated E (exit) site is the site from which discharged tRNAs leave the ribosome. The mRNAbinding site binds a particular nucleotide sequence near the 5’ end of the mRNA, placing the mRNA in the proper position for the translation of its first codon. (a) The diagrammatic representation of a ribosome. The pair of horizo
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