蛋白质的生物合成—翻译 遗传密码 由3个连续的核苷酸组成
蛋白质的生物合成——翻译 • 遗传密码 由3个连续的核苷酸组成
蛋白质的生物合成翻译 蛋白质合成过程 I氨基酸活化 Ⅱ蛋白质合成的起始 AUG→甲酰化甲硫氨酸(fMet) Ⅲ蛋白质合成的终止 终止码UAA、UGA、UAG
蛋白质的生物合成——翻译 • 蛋白质合成过程 Ⅰ.氨基酸活化 Ⅱ.蛋白质合成的起始 AUG→甲酰化甲硫氨酸（fMet) Ⅲ.蛋白质合成的终止 终止码UAA、UGA、UAG
ribosome subunits mRNA released transcript 3 start stop e Ny polypeptides 2 y3 chain released
In the cytoplasmic regions of protein synthesis concentrated pools of amino acids, tRNAs, and ribosomal subunits exist 1. Several proteins (called initiation factors) catalyze the binding of an initiator IRNA to the P ste on a small ribosomal subunit 2. The subunt binds near the 5 end ot an mRNA transcript he anticodon(UAC af the tANA becomes aligned with the start codon (AUG)on the 3. A large ribosomal subunit binds with the small one to form an nitiation comple
mRNA NA binding sit IRNA5 tRNA tRNA binding Dinding initation transcr pt loaded on 1. This diagram shows 2. Once the initiator 3. The anticodon of the an intact the relative positions of tRNA s aligned in second tRNA base pairs the binding sites for the P site. anotho with the second codon tANAs and the mRNA tRNA can occupy an As it does its attached transcript on an intact adjacent binding site (the amino acid aligns with A site) Which particular the amino acid of the tRNA binds is dictated by initator IRNA. the next mRNA codon UGG agGG 4. The bond between the 5. The tRNA hoiding the 6. The anticodon of a third initiator tRNA and its two amino acids moves tRNA base-pairs with the amino acid is broken nto the P: site. The third codon: A peptide bond A peptide bond forms ribosome also moves along forms between amino acids 2 between the two amino the mRNA. so that the and 3. Through repeats of these acids. The initiator tRNA third codon becomes aligned steps, a polypeptide chain grows dissociates from the P site above the A site until a stop codon in the mANA is reached. Then the chain is released