Lecture 23 - 030211

Lecture 23 - 030211 - Lecture 23 Nucleotide Biosynthesis...

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0 Lecture 23 Nucleotide Biosynthesis (II)
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1 Synthesis of DNA A,G,C, U A,G,C, T Ribonucleoside diphosphate deoxyribonucleoside diphosphate Ribonucleotide reductase 1’ 2’ 3’ 4’ 5’
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2 Synthesis of DNA
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3 Ribonucleotide Reductase in E. coli Accept an e - from a Cys in the active site 3 conserved Cystein
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4 Ribonucleotide Reductase in E. coli • A stable tyrosyl radical contains an unpaired electron delocalized onto its aromatic ring •Generated by a nearby iron center: •Two ferric Fe 3+ •One oxide ion O 2-
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5 Ribonucleotide Reductase in E. coli •One Cys transfers an e - to the tyrosyl radical in R2 •Form a highly reactive cysteine thiyl radical Cys Cys Cys Glu
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6 Ribonucleotide Reductase in E. coli •cysteine thiyl radical attracts a proton from C-3’ of the ribose •Forms a radical at C-3’
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7 Ribonucleotide Reductase in E. coli •The C-3’ radical promotes release of OH - from C-2’ • OH - + proton from 2 nd Cys => H 2 O •Glu protonated
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8 Ribonucleotide Reductase in E. coli •3 rd Cys transfers a hydride ion (one proton and two e - ) to complete reduction at C-2’ •Form a disulfide bond •Glu deprotonated to re-form a C-3’ radical
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This note was uploaded on 08/15/2011 for the course CHEM 114B taught by Professor Wang during the Spring '09 term at UCSD.

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Lecture 23 - 030211 - Lecture 23 Nucleotide Biosynthesis...

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