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Protein subunit designated RpoB RpoB is a big protein subunit
= 1178 amino acids • All bacteria have a rpoB gene encoding a RpoB protein, eg. E. coli • RifS wild-type M. tuberculosis and RifR mutant M. tuberculosis exhibit
the following differences that can be explained by spontaneous
mutation: Wild-type RifS Mutant RifR rpoB gene DNA 5'-CAC-3'
3'-GTG-5' Mutation 5'-CGC-3'
3'-GCG-5' mRNA 526th codon 5'-CAC-3' 5'-CGC-3' His Arg RpoB protein
526th amino acid • Even though an amino acid in RpoB changed, RNA polymerase still
works, rifampin just doesn’t bind to it.
• So bacterium is viable and RifR. Parent A
T DNA encoding
526th codon of rpoB
T Wild type
T Wild type
RifS Mismatch eliminated
Mutation stabilized • DNA polymerase has a “proof-reading” ability: can detect basepairing errors and correct them C T
New DNA 5' T AGG
3' DNA Polymerase TCCG TCAG TCAG 5' DNA Template New DNA 5' 3'
A G G 3' T C C G DNA Polymerase C
T C A G T C A G 5' DNA Template In the end…
the error rate is about 1 for every 2 x 109 base pairing events. Stated anothe...
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This note was uploaded on 10/25/2013 for the course MICB 201 taught by Professor Davidturner during the Fall '12 term at UBC.
- Fall '12