RpoB
Encyclopedia
rpoB is a bacterial gene
that codes for part of an enzyme
which synthesises RNA. Specifically, rpoB is the β subunit of the bacterial RNA polymerase
. It is the subunit
which possesses the polymerase
activity, that is, it catalyzes the synthesis of RNA. Some anti-bacterial drugs (most importantly, rifampicin
) kill bacteria by targeting this enzyme.
rpoB is a highly conserved enzyme contained by many bacteria, including Mycobacterium tuberculosis
. It is the target of the antibiotic, rifampicin
. Mutations in this gene are the main mechanism of resistance to rifampicin.
A probe for rpoB can detect mutations in the gene that confer rifampicin resistance. For Mycobacterium tuberculosis, the resistance-mutations most commonly found are at codons 531, 526 and 516 (in decreasing order of frequency), in an area known as the "rifampicin resistance determining region". For Staphylococcus aureus
, the most commonly identified mutation is at codon 481. Gene probes are commonly used to guide tuberculosis treatment
when drug-resistant tuberculosis is suspected.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
that codes for part of an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
which synthesises RNA. Specifically, rpoB is the β subunit of the bacterial RNA polymerase
RNA polymerase
RNA polymerase is an enzyme that produces RNA. In cells, RNAP is needed for constructing RNA chains from DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses...
. It is the subunit
Protein subunit
In structural biology, a protein subunit or subunit protein is a single protein molecule that assembles with other protein molecules to form a protein complex: a multimeric or oligomeric protein. Many naturally occurring proteins and enzymes are multimeric...
which possesses the polymerase
Polymerase
A polymerase is an enzyme whose central function is associated with polymers of nucleic acids such as RNA and DNA.The primary function of a polymerase is the polymerization of new DNA or RNA against an existing DNA or RNA template in the processes of replication and transcription...
activity, that is, it catalyzes the synthesis of RNA. Some anti-bacterial drugs (most importantly, rifampicin
Rifampicin
Rifampicin or rifampin is a bactericidal antibiotic drug of the rifamycin group. It is a semisynthetic compound derived from Amycolatopsis rifamycinica ...
) kill bacteria by targeting this enzyme.
rpoB is a highly conserved enzyme contained by many bacteria, including Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...
. It is the target of the antibiotic, rifampicin
Rifampicin
Rifampicin or rifampin is a bactericidal antibiotic drug of the rifamycin group. It is a semisynthetic compound derived from Amycolatopsis rifamycinica ...
. Mutations in this gene are the main mechanism of resistance to rifampicin.
A probe for rpoB can detect mutations in the gene that confer rifampicin resistance. For Mycobacterium tuberculosis, the resistance-mutations most commonly found are at codons 531, 526 and 516 (in decreasing order of frequency), in an area known as the "rifampicin resistance determining region". For Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
, the most commonly identified mutation is at codon 481. Gene probes are commonly used to guide tuberculosis treatment
Tuberculosis treatment
Tuberculosis treatment refers to the medical treatment of the infectious disease tuberculosis .The standard "short" course treatment for TB is isoniazid, rifampicin , pyrazinamide, and ethambutol for two months, then isoniazid and rifampicin alone for a further four months...
when drug-resistant tuberculosis is suspected.