Ribosome, aminoacyl-tRNA synthetases, genetic code, initiation/elongation/termination.
Translation
Translation
Ribosome-catalysed synthesis of polypeptide from mRNA template, decoded via aminoacyl-tRNAs. Initiation, elongation (peptidyl transfer +…
Ribosome
Universal ribozyme decoding mRNA and catalysing peptide-bond formation. Bacterial 70S = 30S + 50S; eukaryotic 80S = 40S + 60S. Peptidyl…
tRNA (transfer RNA)
~76-nt cloverleaf adaptor with 3′-CCA-A(A) acceptor arm (charged by aminoacyl-tRNA synthetases) and anticodon loop (pairs with mRNA codon).…
Aminoacyl-tRNA synthetase
Family of 20 enzymes (one per amino acid) that charge cognate tRNAs: aa + ATP + tRNA → aa-tRNA + AMP + PPi. Fidelity via editing domains;…
Genetic code
61 sense codons → 20 amino acids (redundant, mostly at 3rd position) + 3 stop codons. Nearly universal with minor variants (mitochondrial,…
Codon-anticodon pairing (wobble)
Watson-Crick pairing at codon positions 1-2 + relaxed (wobble) pairing at position 3 (Crick 1966) — explains codon redundancy with <64 tRNA…
Translation initiation
Bacterial: Shine-Dalgarno + fMet-tRNA + IF1-3. Eukaryotic: cap-dependent scanning (eIF4F + 40S·Met-tRNA·eIF2·GTP) from 5′ cap to…
Peptide-bond formation
Peptidyl transfer reaction catalysed by 23S/28S rRNA at the peptidyl-transferase centre. Nucleophilic attack by A-site α-amino on P-site…
Translation elongation
EF-Tu delivers aa-tRNA; peptidyl transferase forms peptide bond; EF-G translocates ribosome. Repeats until stop codon. ~20 aa/sec in…
Translation termination
Stop codon UAA/UAG/UGA recognised by release factors (RF1/2 bacterial, eRF1 eukaryotic) which hydrolyse the peptidyl-tRNA bond. Ribosome…