MCB 450 1st Edition Lecture 25 Outline of Last Lecture I Ribosomal RNA processing II tRNA processing III mRNA processing IV RNA binding proteins V The genetic code VI Wobble hypothesis VII tRNA structure VIII tRNA anticodon binding to codon IX Aminoacyl tRNA synthetase Outline of Current Lecture I Ribosomal subunits II Initiation complex formation III Elongation IV Termination V Prokaryotic vs eukaryotic protein synthesis VI Synthesis of secreted proteins VII Regulation of protein synthesis VIII Mutations Current Lecture Wobble Hypothesis Only the third pair is wobbly and not as strict with which base it pairs Wobble hypothesis for degeneracy of the genetic code G is the only base that doesn t pair with I Covalent linkage of amino acid to cognate tRNA Ester bond between amino acid and tRNA Formylation of met tRNA in E coli Methionine only has one codon but has two tRNA Charging of tRNAs Need to have a way to correct this error this is done by synthetase Recognition sites on tRNA for synthetase These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Synthetase will recognize the right tRNA by looking a specific sites along the tRNA Specificity of the threonine synthetase Threonine and serine have hydroxyl groups that can interact with the zinc Valine will not interact with the zinc Double sieve model of editing by aminoacyl tRNA synthetase The correct amino acid will be too big to enter the editing site and thus will not be removed A smaller amino acid will enter the editing site though and will get removed Indicates that it was the wrong amino acid The ribosome has three binding sites for tRNAs Decoding center is where the mRNA binds Initiation Site purine rich UAC anticodon of initiator tRNA at P site 16S rRNA AUUCCUCCA EF Tu brings charged tRNA to appropriate codon Must be recharged with a new GTP molecule Which is done by EF T Covalent linkage of amino acid to cognate tRNA Ester bond between amino acid and tRNA Peptide bond formation Amino group of the amino acid is free and will attack the carboxyl group
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