Translation in prokaryotes

1. By: MARYAM SHAKEEL TRANSLATION IN PROKARYOTES

2. TRANSLATION: The process in which the messenger RNA (mRNA) generated by transcription is interpreted by the ribosome to generate a particular amino acid succession, or polypeptide that will fold into an active protein. STAGES:

3. Bringing the Small Ribosomal Subunit to the Initiation Codon Binding of small ribosomal subunit to the initiation codon at m-RNA. How small subunit of ribosomes select initiation codon Initiation factors IF1,IF2,IF3 INITIATION Shine- Dalgarno Sequence

4. Bringing the first aa-tRNA into the ribosome AUG is an initiation and only one codon for METHIONINE. t-RNA enter at P site and bind to both AUG & IF2 Assemble complete Initiation complex Larger subunit join complex GTP hydrolyse IF2-GDP release It is always first amino acid in polypeptide chain

5. Aminoacyl -t RNA Selection Entry of second aminoacyl-tRNA in A site EF- Tu is require to deliver aminoacyl-tRNA to A site Complex of aminoacyl-tRNA Tu -GTP enter GTP is hydrolyse and Tu -GTP release ELONGATION Must join EF- Tu bound to GTP Series of steps is repeated over and over as amino acids are polymerised in growing polypeptide chain

6. Peptide Bond Formation Two amino acid, attached with separate tRNA are juxtaposed in such position that the can react Amine nitrogen of the aa-tRNA in A site carries out a nucleophilic attack on carbonyl carbon of amino acid bound to tRNA of P site

7. As a result tRNA at A site Dipeptide tRNA in P site deacylated A component of large ribosomal subunit known as ribozyme .

8. TRANSLOCATION It is actually characterized by a ratchet-like motion of ribosomes Dipeptidyl-tRNA shift from A site P site GTP hydrolyse and EF-G-GDP leaves Ribosomes moves three nucleotide along mRNA in 5’-3’ direction

9. Releasing the Deacylated tRNA Deacylated tRNA leaves ribosome Empty E site

10. STOP CODON Class 1 RFs RF1, RF2 Class 2 RFs GTP binding protein TERMINATION Release Factor

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