Post on 22-Dec-2015
Components of Translation
Amino acidsThe tRNAAminoacyl-tRNA synthetasesThe mRNACompetent ribosomesProtein factorsATP and GTP
Protein Biosynthesis
Translation:Genetic code on mRNA to amino acids on proteins
Polycistronic Vs Monocistronic
Steps:InitiationElongationTermination
Posttranslational modifications
Protein Biosynthesis: Initiation
Complementarity: 5’-end mRNA and 3’-end 16S rRNA
Shine-Dalgarno sequence
Protein Biosynthesis: Initiation-2
Initiation complexAssembly of components of translation:
The mRNA2 Ribosomal subunitsAminoacyl-tRNAGTPInitiation factors (IF or eIF)
Protein Biosynthesis: Initiation-3
Initiation codonAUG for metthionine
Initiator tRNA: IF-2 and P-site
N-Formylated methionine:
Transformylase
N10-formyl tetrahydrofolate
After binding to tRNA
Removal of N-formyl methionine
Protein Biosynthesis: Elongation
Addition of amino acids to the carboxyl end
Elongation factors: EF-Tu, EF-Ts (eEF)
Peptidyltransferase: 23S rRNA (ribozyme) and GTP
Translocation: Ribosome moves in 5’-3’ on mRNAEF-G and GTPMovement of uncharged tRNA to E-siteMovement of peptidyl-tRNA to P-site
Protein Biosynthesis: Termination
Termination codons at the A-site
RF-1: UAA and UAGRF-2: UAA and UGARF-3: Binds GTP
Termination:Release of newly synthesized polypeptideDissociation of ribosome from mRNARecycling: Ribosomal subunits
mRNA and tRNAprotein factors
eRF: Single release factorBinds GTP