Sigma factor: Difference between revisions

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The <scene name='59/591940/Transcription_bubble/1'>transcription bubble</scene>, also referred to as the '''open complex''' is formed through the common '''housekeeping σ factors''' which unwind about 13 bp of duplex DNA in an ATP independent process. Research has shown that σ factors require invariant basic and aromatic residues (Phe, Tyr, Trp) critical for this formation. The process of bubble formation begins at the -11 formation (usually A) and propogates to +1 site, through a phenomenon called <scene name='59/591940/Transcription_bubble_flipped/1'>Base Flipping</scene>, which interrupts the stacking interactions stabilizing the double helix conformation. As this process occurs and the DNA transitions into the open promoter complex, certain RNAP-σ contacts are lost, initiating the dissociation of σ. In summary, the processes of -35 and -10 motif sequence recognition and helix strand separation are coupled by the σ factor.

===~~Restriction~~===

==Restriction==

Normally, σ-factor domains cannot bind to promoters. These domains usually are placed in very compacted positions relative to each other, a conformation that buries DNA-binding determinants. This type of restriction is called '''conformational restriction'''. Additionally, in housekeeping σs, a domain called the '''σ(1.1)''' stabilizes the compact conformation mentioned above, thereby preventing any promoter recognition.

Initiation of prokaryotic transcription requires cooperation between the σ peptide and RNAP. Without these interactions, no transcription is possible.

===Comformational and Autoinhibitory===

Normally, σ-factor domains cannot bind to promoters on their own. These domains usually are placed in very compacted positions relative to each other, a conformation that buries DNA-binding determinants. This type of restriction is called '''conformational restriction'''. Additionally, in housekeeping σs, a domain called the '''σ(1.1)''' stabilizes the compact conformation mentioned above, thereby preventing any promoter recognition. This method of restricting the binding abilities of isolated σ's is called '''autoinhibitory inhibition'''.

===anti-σ's===

Sigma factor: Difference between revisions

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@@ Line 16: / Line 16: @@
 The <scene name='59/591940/Transcription_bubble/1'>transcription bubble</scene>, also referred to as the '''open complex''' is formed through the common '''housekeeping σ factors''' which unwind about 13 bp of duplex DNA in an ATP independent process.  Research has shown that σ factors require invariant basic and aromatic residues (Phe, Tyr, Trp) critical for this formation.  The process of bubble formation begins at the -11 formation (usually A) and propogates to +1 site, through a phenomenon called <scene name='59/591940/Transcription_bubble_flipped/1'>Base Flipping</scene>, which interrupts the stacking interactions stabilizing the double helix conformation.  As this process occurs and the DNA transitions into the open promoter complex, certain RNAP-σ contacts are lost, initiating the dissociation of σ.  In summary, the processes of -35 and -10 motif sequence recognition and helix strand separation are coupled by the σ factor.
-===Restriction===
+==Restriction==
-Normally, σ-factor domains cannot bind to promoters.  These domains usually are placed in very compacted positions relative to each other, a conformation that buries DNA-binding determinants.  This type of restriction is called '''conformational restriction'''.  Additionally, in housekeeping σs, a domain called the '''σ(1.1)''' stabilizes the compact conformation mentioned above, thereby preventing any promoter recognition.
+Initiation of prokaryotic transcription requires cooperation between the σ peptide and RNAP.  Without these interactions, no transcription is possible.
+===Comformational and Autoinhibitory===
+Normally, σ-factor domains cannot bind to promoters on their own.  These domains usually are placed in very compacted positions relative to each other, a conformation that buries DNA-binding determinants.  This type of restriction is called '''conformational restriction'''.  Additionally, in housekeeping σs, a domain called the '''σ(1.1)''' stabilizes the compact conformation mentioned above, thereby preventing any promoter recognition.  This method of restricting the binding abilities of isolated σ's is called '''autoinhibitory inhibition'''.
 ===anti-σ's===