Translation

• Synthesis of proteins as directed by mRNA templates

  Translation
• Transmits information present in DNA

  mRNA
• Acts a bilingual translator molecule

  tRNA
• Workbenches for protein synthesis

  Ribosomes and rRNA
• serve to mediate the attachment of specific amino acids to specific tRNA molecules

  tRNA synthetases
• adaptors that align amino acids on the mRNA template

  transfer rna
• nucleotide sequence of transfer rna that forms complementary base pairs with a codon sequence of messenger rna

  anticodon
• enzyme that joins a specific amino acid to a tRNA molecule carrying the correct anticodon sequence

  aminoacyl tRNA synthetase
• sequence to which the amino acid is bound, the encoded amino acid covalently attaches to the ribose of the terminal adenosine

  3'-terminal-CCA
• common structural components


  conserved cloverleaf secondary structure
• common structural components


  l-shaped three dimensional structure
• allow tRNA to incorporate the correct amino acid into the growing protein chain

  anticodon
• incorporation of the correct amino acid into the protein

  proper amino acid attaching to tRNA
• process of synthetase attaching to amino acid 


  activation of the amino acid with amp, attachment of the amino acid rna
• composed of rna and proteins that are the sites of protein synthesis

  ribosome
• passage for mrna


  large ribosomal subunit
• tunnel for emerging peptide

  small ribosomal subunit
• facilitate the coupling of tRNA anticodons with mRNA codons

  ribosome
• transcribed in the nucleus, bind to special proteins to form the ribosomal subunits in the nucleolus


  rRNA
• forms a ribosome only when they attach to an mRNA molecule


  large and small subunits
• methionine


  aug
• tryptophan 


  ugg
• multiple codons for a single amino acid

  degeneracy in the code
• nearly universal


  genetic code
• arginine


  aga, agg
• isoleucine

  aua
• termination

  uga
• translation of mrna


  direct interaction with complementary anticodon sequence in trna
• carries a unique amino acid, three-base anticodon sequence

  trna
• codon-anticodon base pairing


  antiparallel
• read in sequential, nonoverlapping reading frame

  codons
• located at opposite extremes of trna

  anticodon and amino acid receptor sites
• process of translation


  initiation - ribosome binds mrna at start codon

  elongation - polypeptide chain adds amino acids

  termination - polypeptide is released and ribosome dissociates (stop codon)
• involved in first translation step in both eukaryotes and prokaryotes

  initiation factors
• initiation in eukaryotes requires

  twelve proteins
• small subunit binds to the cap of mrna and moves to the first aug codon


  eukaryotes
• internal ribosome entry site in the middle

  viral mrna
• small subunit binds to a shine-dalgarno sequence anywhere in mrna to initiate translation

  bacteria
• produced from an operon

  polycistronic
• elf1a and elf3


  binds to 40s subunit