Termination processor protein synthesis is performed by all except: (PGI May 2010)
Correct Answer: Peptidyl transferase
Description: Ans: C (Peptidyl transferase) & E(AUG codon) AUG is initiation codon while UAA,UAG & UGA are termination codon"- Chatterjea & Shinde 7th/249-50"Peptidyl transferase catalyses peptide bond formation"- Harper 28th/362"In most of cases, AUG acts as initiator codon. AUG also acts as codon for methionine. In a few proteins, GUG may be initiator codon -Vasudevan 5th/431Termination Process of Protein Synthesis Vasudevan 5th/433After successive addition of AA, ribosome reaches the terminator codon sequence on mRNA. Since there is no tRNA bearing the corresponding anticodon sequence, the "A" site remains freeReleasing factor(RF) enters the site along with hydrolysis of GTP to GDP. The RF hydrolyses the peptide chain from the tRNA at P site. The completed peptide chain is now released. Finally 80S ribosome dissociates into its component units of 60S & 40S.Materials Required for Protein SynthesisAmino acidsDNA & 3 RNAs (m-RNA, t-RNA, r-RNA)Polyribosomes (polysomes)QEnzymes: Aminoacyl-t-RNA synthetase, peptidyl transferaseFactorsInitiation facors- IF1 to 3(For prokaryotes)10 elF (elF-1, elF-2, elF-3, elF-4A, elF-4B, e!F-4G, elF- 4E, elf-5Q, for eukaryotes)Elongation factors-EFl & EF2QRelease factors R1 & R2Coenzymes & cofactors. FH4 Mg2+EnergyATP, GTPQ
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