BBMB 405 1nd Edition Lecture 34 Outline of Last Lecture XVI Chapter 30 Protein Synthesis C The ribosome is the site of protein synthesis Outline of Current Lecture XVI Chapter 30 Protein Synthesis D Eukaryotic protein synthesis differs from prokaryotic protein synthesis primarily in translation initiation E A variety of antibiotics and toxins can inhibit protein synthesis F Ribosomes bound to endoplasmic reticulum manufacture secretory and membrane proteins XVII Chapter 31 The control of gene expression in prokaryotes A Introduction Current Lecture XVI Chapter 30 Protein Synthesis D Eukaryotic protein synthesis differs from prokaryotic protein synthesis primarily in translation initiation 1 Selenocysteine the 21st amino acid a Lower pka so deprotonated at body pH has a lower reduction potential b Used in antioxidants c Binds to stop codon can bind to tRNA like cysteine 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 2 Cap independent translation a Internal Ribosome Entry Site IRES is recognized by translation components and is translated b Direct recruitment of 40S of eIFs c Often found in viruses hijack cellular translation machinery d Cellular mRNAs involved in stress response E A variety of antibiotics and toxins can inhibit protein synthesis 1 Inhibition of protein synthesis a potent drug target a Streptomycin highly basic interferes with ability of initiator tRNA to bind to 30S subunit b Puromycin mimics aminoacyl tRNA and can be incorporated at end of nascent peptide 2 Ricin cleaves 28S rRNA and renders ribosome inactive a Deadly toxin single molecule can kill cell extracted from castor beans b Two protein chains chain B binds cell surface and injects toxin chain A cleaves sarcin ricin loop of 28S rRNA F Ribosomes bound to endoplasmic reticulum manufacture secretory and membrane proteins 1 Synthesis of secretory and membrane proteins a Ribosomes must be directed to membranes for insertion or secretion b In eukaryotes ribosomes are directed to rough endoplasmic reticulum 2 A signal sequence marks proteins for translocation across the ER membrane 3 The signal sequence is recognized by signal recognition particle SRP a SRP binds signal sequence as it emerges from ribosome b SRP diffuses to ER and binds to SRP receptor c SRP targeting to membrane process dependent on GTP hydrolysis d 4 Transport vesicles refer to picture below a Most membrane proteins will already be inserted into membrane of vesicle protein inserted in plasma membrane b Signal traffic proteins to lysosome lysosome c Protein modification cis golgi d XVII Chapter 31 The control of gene expression in prokaryotes A Introduction 1 Regulation of gene expression a What factors control gene expression b DNA Cis regulatory elements trans acting factors epigenetic control c RNA processing degradation sequenstration d Protein modification degradation 2 Gene regulation in prokaryotes vs eukaryotes transcription a General prokaryotic features operon structures polycistronic transcripts no mRNA processing activators and repressors b General eukaryotic features operon structures uncommon monocistronic transcripts mRNA processing activators and repressors 3 The lac operon a classic example of transcriptional regulation
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