Rifampicin and Rifabutin
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Rifampicin acts on the β subunit of RNA polymerase. Binding of just one molecule of rifampicin inhibits the initiation stage of transcription in which the first nucleotide is incorporated in the RNA chain.
Rifampicin And Rifabutin
Rifampicin acts on the β subunit
of RNA polymerase. Binding of just one molecule
of rifampicin inhibits
the initiation stage of transcription in which the first nucleotide is incorporated in the RNA chain.
Once started, transcription
itself is not inhibited. It has been suggested
that the structure of
rifampicin resembles that of two
adenosine nucleotides in RNA; this may form the basis of the binding
of the antibiotic to the β subunit.
One problem is the rapid
development of resistance in organisms due to alterations in the amino
acids comprising one particular
region of the β subunit.
These changes do not
affect the activity of the polymerase but render it insensitive to rifampicin. The
action of rifampicin is specific for the
microbial RNA polymerase, the mammalian version being unaffected. Rifabutin, which has enhanced
activity against Mycobacterium avium
complex, is thought
to act in the same way as rifampicin.
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