Initial amino acid in prokaryotic protein synthesis –
Correct Answer: Formyl-methionine
Description: Ans. is 'c- i.e., Formyl-methionine o in prokaryotes and in mitochondria, the first amino acid methionine is modified by formylation, i.e. the initiator t-RNA carries an N-formylated methionine. The formyl group is added by the enzyme transformylase (formyl- transferase). In Eukaryotes, the initiator t-RNA carries a methionine that is not formylatedDifferenceProkaryotesEukaryotesm-RNAPolycistronic i.e. have several coding regions; each with its initiation & termination codon producing a seperate polypeptideMonocistr onic with one coding regionAmino acid incorporation rate18 aa/sec6aa/sec.Initial amino acidFormylated methionine ( f-met)Methionine r (Met)Initial t-RNAt-RNA/MettRNAMetTranscription & translationTranslation starts before transcription is ended (coupled)UncoupledInitiation factors (IF)3i.e.IF1,IF2,IF3> 10 designated elFDetermination of initiatingcodon# Shine Dalgarno sequencer# Facilitated by IF-2 bound to GTPKozak consensus sequencesr Facilitated by elF-2 bound to GTP (Plus additional elF)Elongation: Del Every of aminoacyl t-RNA to A site# Facilitated by EF-Tu & EF-TsFacilitated by EF1 a and EF 1 b yNucleotide exchange factors# EF - Ts (as it exchanges its GTP for GDP on EFTu)EF 1 b g (as it exchanges its GTP forGDP on EF a)Peptidyi transferase activity catalyzing peptide bond formation23 S rRNA of 50 S ribosomal subunit (ribozyme)28 S rRNA of 60 S ribosornal subunit (ribozyme)TranslocationRequires EF-G & GTPRequires EF-2 & GTPTerminationRelease factor (RF) 1 recognizes UAA & UAG, RF2 recognizes UAA & UGARF-3 (bound to GTP) causes release ofRF-1 or RF-2 as GTP is hydrolysedeRF recognizesail 3 UAA, UAGandUGA and release nascent polypeptide chaineRF-3 (bound to GTP) function like prokaryotic RF-3 & release eRF
Category:
Biochemistry
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now