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• Causes “ fire-blight” disease of B.C. orchard fruits.
• Secretes extracellular enzyme that digests fruit tissue • Streptomycin sprayed on orchards in large quantities to kill E.
• Streptomycin binds to
one of the proteins
making-up the small
subunit of bacterial
translation. • Small protein
• Protein designated
RpsL • All bacteria have a rpsL gene encoding a RpsL protein, eg. E. coli • StrS wild-type E. amylovora and StrR mutant E. amylovora exhibit the
following differences that can be explained by induced mutation: Wild-type StrS
rpsL gene DNA
mRNA 43rd codon
43rd amino acid Mutant StrR 5'-AAA-3' Mutation 5'-AGA-3'
Lys Arg • Even though an amino acid in RpsL has been changed by mutation
in rpsL, the ribosome still works, streptomycin just doesn’t bind to it.
• So bacterium is viable and StrR. “A” base damaged
by chemical that
an amino group.
“AD” resembles “G” Parent 1st
3’-T T T-5’
43rd codon of rpsL AD
generation Depends on
T Wild type
T Wild type
StrS Mismatch eliminated
Mutation stabilized • Repair of DNA with damaged bases
• Example: C base damaged by
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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