BBMB 405 1st Edition Lecture 23 Outline of Last Lecture XVIII Chapter 26 The Biosynthesis of Membrane Lipids and Steroids D Important derivatives of cholesterol include bile salts and steroid hormones Outline of Current Lecture XIV Chapter 28 DNA Replication Repair and Recombination A Introduction Central Dogma and Review B DNA replication proceeds by polymerization of deoxyribonucleoside triphosphates along template Current Lecture XIV Chapter 28 DNA Replication Repair and Recombination A Introduction Central Dogma and Review 1 DNA transcribed to RNA is translated to Protein 2 Types of polymerases a DNA dependent DNA polymerase replication b DNA dependent RNA polymerase transcription c RNA dependent DNA polymerase reverse transcription d RNA dependent RNA polymerase RNA replication 3 Requirements of polymerases Template dNTPs or NTPs metal ions DNA also requires a primer 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 4 DNA structure review right handed helix 10 to 10 5 pairs per turn minor grove lead to non specific reacitons and major grove directionality 5 to 3 5 DNA replication is semi conservative 6 What are requirements for DNA replication Template speed processivity fidelity repair 7 DNA must be accurately replicated and maintained 1 Errors can occur during replication via incorrect incorporation 2 DNA damage can occur at any time 3 8 DNA polymerase review need to have triphosphate because if primary phosphate is hydrolyzed then polymerase stalls B DNA replication proceeds by polymerization of deoxyribonucleoside triphosphates along template 1 2 Fingers are nucleotide binding ssDNA template interaction 3 Palm has catalytic residues and is where DNA sits 4 Thumb is dsDNA product interaction 5 Two metal ion mechanism of DNA polymerase metal is activated nucleophile for attack on phosphate 6 Considerations for fidelity of DNA polymerase a Nucleotide misincorporation errors occur at rate of 10 5 bp for DNA polymerase III b Mismatch Extension errors are missed by DNA pol III proofreading at rate of 10 2 bp c Overall error rate of DNA pol III is 10 7 bp 7 What determines if aquired correct nucleotide for binding Shape of nucleotide 8 Why shapte complementarity so important Residues Arg and Gln of enzyme form hydrogen bonds in minor groove side of base pair in active site The hydrogen bond acceptors act as ruler that measure if properly spaced base pair has formed in active site DNA polymerases close down around incoming dNTP the binding triggers conformational change where finger domain rotates to form tight pocket into which only properly shaped base pair fits 9 Model of DNA binding to two active sites a Primer strand can transfer between polymerase and 3 5 exonuclease active sites b Destabilized dsDNA favors editing complex 10 Note rest of notes from this lecture overlap with next lecture if they are not in this lecture s notes they are in next lecture s notes
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