17. 2011-02-23

Protein subunit designated rpob rpob is a big protein

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Unformatted text preview: tion. 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 5’-CAC-3’ 3’-GTG-5’ A T Base-pairing error 2nd generation 1st generation A T A T Wild type RifS Wild type RifS G C G T Mismatch Mutation Mutant RifR A 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.

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