difference between sigma factor and rho factor
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Rho factor
Aρ factor (Rho factor) is a prokaryotic proteininvolved in the termination of transcription. Rho factor binds to the transcription terminator pause site, an exposed region of single stranded RNA (a stretch of 72 nucleotides) after the open reading frame at C-rich/G-poor sequences that lack obvious secondary structure.
Rho factor is an essential transcription protein in prokaryotes. In Escherichia coli, it is a ~274.6 kD hexamer of identical subunits. Each subunit has an RNA-binding domain and an ATP-hydrolysis domain. Rho is a member of the family of ATP-dependent hexameric helicases that function by wrapping nucleic acids around a single cleft extending around the entire hexamer. Rho functions as an ancillary factor for RNA polymerase.
Sigma factor
A sigma factor (σ factor) is a protein needed for initiation of transcription in bacteria. It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase(RNAP) to gene promoters. It is homologous to archaeal transcription factor B and to eukaryotic factor TFIIB.The specific sigma factor used to initiate transcription of a given gene will vary, depending on the gene and on the environmental signals needed to initiate transcription of that gene. Selection of promoters by RNA polymerase is dependent on the sigma factor that associates with it.
The sigma factor, together with RNA polymerase, is known as the RNA polymerase holoenzyme. Every molecule of RNA polymerase holoenzyme contains exactly one sigma factor subunit, which in the model bacterium Escherichia coli is one of those listed below. The number of sigma factors varies between bacterial species. E. colihas seven sigma factors. Sigma factors are distinguished by their characteristic molecular weights. For example, σ70 is the sigma factor with a molecular weight of 70 kDa.
The sigma factor in the RNA polymerase holoenzyme complex is required for the initiation of transcription, although once that stage is finished, it is dissociated from the complex and the RNAP continues elongation on its own.
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Rho factor
Aρ factor (Rho factor) is a prokaryotic proteininvolved in the termination of transcription. Rho factor binds to the transcription terminator pause site, an exposed region of single stranded RNA (a stretch of 72 nucleotides) after the open reading frame at C-rich/G-poor sequences that lack obvious secondary structure.
Rho factor is an essential transcription protein in prokaryotes. In Escherichia coli, it is a ~274.6 kD hexamer of identical subunits. Each subunit has an RNA-binding domain and an ATP-hydrolysis domain. Rho is a member of the family of ATP-dependent hexameric helicases that function by wrapping nucleic acids around a single cleft extending around the entire hexamer. Rho functions as an ancillary factor for RNA polymerase.
Sigma factor
A sigma factor (σ factor) is a protein needed for initiation of transcription in bacteria. It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase(RNAP) to gene promoters. It is homologous to archaeal transcription factor B and to eukaryotic factor TFIIB.The specific sigma factor used to initiate transcription of a given gene will vary, depending on the gene and on the environmental signals needed to initiate transcription of that gene. Selection of promoters by RNA polymerase is dependent on the sigma factor that associates with it.
The sigma factor, together with RNA polymerase, is known as the RNA polymerase holoenzyme. Every molecule of RNA polymerase holoenzyme contains exactly one sigma factor subunit, which in the model bacterium Escherichia coli is one of those listed below. The number of sigma factors varies between bacterial species. E. colihas seven sigma factors. Sigma factors are distinguished by their characteristic molecular weights. For example, σ70 is the sigma factor with a molecular weight of 70 kDa.
The sigma factor in the RNA polymerase holoenzyme complex is required for the initiation of transcription, although once that stage is finished, it is dissociated from the complex and the RNAP continues elongation on its own.
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Transcription factor
Explanation:
- Sigma factor is the initiation factor that helps the RNA polymer ase bind with the promoter end of the DNA strand and begins transcription. Rho factor binds with the RNA polymerase upon reaching the termination region and help it to 'fall off' the DNA strand, so does the nascent, or prepared, RNA
- Rho factor on the other hand is a protein which binds to the transcription terminator pause site and hence is responsible for termination of transcription.
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