清华大学：《分子生物学》课程PPT教学课件（基因ene）第六章 蛋白质合成（Protein synthesis）

Chapter 6 Protein synthesis 清莘大当

Chapter 6 Protein synthesis

6.1 Introduction 6.2 The stages of protein synthesis 6.3 Initiation in bacteria needs 30S subunits and accessory factors 6.4 A special initiator tRNA starts the polypeptide chain 6.5 Initiation involves base pairing between mRNA and rRNA 6.6 Small subunits scan for initiation sites on eukaryotic mRNA 6.7 Eukaryotes use a complex of many initiation factors 6.8 Elongation factor T loads aminoacyl-tRNA into the A site 6.9 Translocation moves the ribosome 6.10 Three codons terminate protein synthesis 6.11 Ribosomes have several active centers 6.12 The organization of 16S rRNA 6.13 23S rRNA has peptidyl transferase activity 清苇大兰

6.1 Introduction 6.2 The stages of protein synthesis 6.3 Initiation in bacteria needs 30S subunits and accessory factors 6.4 A special initiator tRNA starts the polypeptide chain 6.5 Initiation involves base pairing between mRNA and rRNA 6.6 Small subunits scan for initiation sites on eukaryotic mRNA 6.7 Eukaryotes use a complex of many initiation factors 6.8 Elongation factor T loads aminoacyl-tRNA into the A site 6.9 Translocation moves the ribosome 6.10 Three codons terminate protein synthesis 6.11 Ribosomes have several active centers 6.12 The organization of 16S rRNA 6.13 23S rRNA has peptidyl transferase activity

6.1 Ribosomes rRNAS Proteins Introduction Bacterial 505 238=2904 bases 31 Figure 6.1 70S 5S=120 bases Ribosomes are large mass:2.5 MDa 66%RNA ribonucleoprotein 309 168=1542 bases 21 particles that contain Mammalian more RNA than 288=4718 bases 60S 5.8S 160 bases protein and 80S 5S =120 bases 49 mass:4.2 MDa dissociate into large 60%RNA and small subunits 409 188=1874 bases 33 清菜大当

Figure 6.1 Ribosomes are large ribonucleoprotein particles that contain more RNA than protein and dissociate into large and small subunits. 6.1 Introduction

30S 6.1 Introduction 509 Figure 6.2 Electron microscopic images of bacterial ribosomes and subunits reveal their shapes.Photographs 70S kindly provided by James Lake. 清苇大当

Figure 6.2 Electron microscopic images of bacterial ribosomes and subunits reveal their shapes. Photographs kindly provided by James Lake. 6.1 Introduction

6.2 The stages of protein synthesis Figure 6.3 Size comparisons 200A show that the ribosome is large 60A enough to bind tRNAs and 220A mRNA. 35 base mRNA 情華大当

Figure 6.3 Size comparisons show that the ribosome is large enough to bind tRNAs and mRNA. 6.2 The stages of protein synthesis

Codon "n" codon "n+1 合8NA Ribosome movement 6.2 The stages of protein synthesis 1 Before peptide bond formation peptidyl tRNA occupies P site,aminoacyltRNA occupies A site Nascent chain Amino acid for codon n+1 2 Peptide bond fomation involves transfer of polypeptide from peptidyl-tRNA in P site to aminoacyl-tRNA in A site Figure 6.4 The ribosome has two 3 Translocation moves ribosom e one codon; places peptidyl-tRr site;deacylated sites for binding tRNA leaves via E site,A site is empty for next aa-tRNA charged tRNA. 清菜大当 Codon "n+1" Codon "n+2

Figure 6.4 The ribosome has two sites for binding charged tRNA. 6.2 The stages of protein synthesis

6.2 The stages of protein synthesis Aminoacyl-tRNA Polypeptide_is transferred to Translocation moves enters the A site aminoacyl-tRNA peptidyR NA into P site Figure 6.5 Aminoacyl-tRNA enters the A site,receives the polypeptide chain from peptidyl-tRNA,and is transferred into the P site for the enxt cycle of elongation. 情莘大当

Figure 6.5 Aminoacyl-tRNA enters the A site, receives the polypeptide chain from peptidyl-tRNA, and is transferred into the P site for the enxt cycle of elongation. 6.2 The stages of protein synthesis

6.2 The stages of protein synthesis tRNA Figure 6.6 tRNA and E site mRNA move P site A site through the ribosome in the same mRNA direction. 清苇大当

Figure 6.6 tRNA and mRNA move through the ribosome in the same direction. 6.2 The stages of protein synthesis

Initiation 30S subunit on mR NA binding site is joine d by 50S subunit and aminoacyl- tRNA binds 6.2 The stages of protein synthesis Elongation Ribosome moves alon g mRNA and length of protein chain extends by transfer from pepti dyl-tRNA to am inoacyl- Figure 6.7 Protein Temination Polypeptide chain is rele ased from tRNA,an d ribosome dissociate s from mRNA synthesis falls into three stages. 情華大当

Figure 6.7 Protein synthesis falls into three stages. 6.2 The stages of protein synthesis

6.2 The stages of protein synthesis mRNA is translated by triplets Figure 5.9 A ribosome assembles from ● its subunits on mRNA, translates the nucleotide triplets into protein,and then dissociates from the mRNA. 清苇大当

Figure 5.9 A ribosome assembles from its subunits on mRNA, translates the nucleotide triplets into protein, and then dissociates from the mRNA. 6.2 The stages of protein synthesis