小结 √在每一个翻译循环的末期，E.coli核糖 体解体为亚基。 √IF1促进了核糖体的解体，而F3结合到 游离的30S亚基上从而阻止了它们与50S 亚基的重新结合形成完整的核糖体
小 结 ✓在每一个翻译循环的末期，E.coli核糖 体解体为亚基。 ✓IF1促进了核糖体的解体，而IF3结合到 游离的30S亚基上从而阻止了它们与50S 亚基的重新结合形成完整的核糖体
Formation of the 30s initiation complex .30s initiation contain 30s ribosome subunit,mRNA,aminoacyl-tRNA,and initiation factors. .The first codon and first aminoacyl- tRNA ·first codon:AUG(90号)，GUG(8号)， and UUG(1号) first aminoacyl-tRNA:tRNA Met,the methionine(甲疏氨酸)formation takes place on the tRNA
Formation of the 30S initiation complex •30S initiation contain 30S ribosome subunit, mRNA, aminoacyl-tRNA, and initiation factors. •The first codon and first aminoacyltRNA • first codon: AUG (90%), GUG(8%), and UUG(1%) first aminoacyl-tRNA: tRNAf Met, the methionine(甲硫氨酸)formation takes place on the tRNA
first aminoacyl-tRNA:tRNA Met Figure 17.8 HOCH, Amino acid! RNase tRNA-CCA-leucine Nucleotides (Adenosyl-leucine OH 亮氨酸腺苷酯 0=d +HN-C-H CH2 H C CH tRNA-CCA-methionine RNase Nucleotides+Adenosyl-methionine (+tRNA-CCA-N-formyl-methionine Adenosyl-N-formyl-methionine 腺苷甲硫氨酸酯+N-腺苷甲酰甲硫氨酸酯 coo coo +H2N-C-H H-C- C-H the tRNA with which they CH2 CH2 CH2 CH2 started was esterified CH3 CH3 Methionine N-formyl-methionine
first aminoacyl-tRNA: tRNAfMet Figure 17.8 Amino acid 亮氨酸腺苷酯 腺苷甲硫氨酸酯+N-腺苷甲酰甲硫氨酸酯 the tRNA with which they started was esterified
小结 √原核生物的起始密码子通常是AUG,但也可 以是GUG,极少数是UUG。 √起始的氨基酰-tRNA是N-甲酰甲硫氨酸- tRNAfMet。因此，合成的多肽链的第一个氨 基酸是fMet, √但是，在蛋白成熟加工过程中fMet是经常 被切除的
小 结 ✓原核生物的起始密码子通常是AUG，但也可 以是GUG，极少数是UUG。 ✓起始的氨基酰-tRNA是N-甲酰甲硫氨酸- tRNAfMet。因此，合成的多肽链的第一个氨 基酸是fMet， ✓但是，在蛋白成熟加工过程中fMet是经常 被切除的
Binding mRNA to the 30s ribosome The initiating codon(AUG,or sometimes GUG or UUG) also occur in the interior of a message.How does the cell detect the difference between an initiation codon and an ordinary codon with the same sequence?Two explanations Either a special primary structure (RNA sequence)or a special secondary RNA structure occurs near the initiation codon that identifies it as an initiation codon and allows the ribosome to bind there
The initiating codon(AUG, or sometimes GUG or UUG) also occur in the interior of a message. How does the cell detect the difference between an initiation codon and an ordinary codon with the same sequence? Two explanations : Either a special primary structure (RNA sequence) or a special secondary RNA structure occurs near the initiation codon that identifies it as an initiation codon and allows the ribosome to bind there. Binding mRNA to the 30S ribosome