RTP and Tus: Difference between revisions
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'''So how does Tus actually stop the replication fork? And why is it a polar arrest mechanism?''' | '''So how does Tus actually stop the replication fork? And why is it a polar arrest mechanism?''' | ||
Mulcair et al (2006) discovered that the key to Tus forming a locked complex with ''Ter'' was twofold: firstly, the locked complex was formed only on the approach of DnaB helicase (the leading edge of the replication fork), and secondly, this locked complex was due to the base-flipping of C6 of ''Ter'' DNA into a cytosine-specific binding pocket on Tus. The approach of DnaB is essential to lock formation as strand separation is required before the C6 base can twist out of the helix. This C6 binds somewhere near the α4 helix, in or near the DNA-binding channel. | Mulcair et al (2006) discovered that the key to Tus forming a locked complex with ''Ter'' was twofold: firstly, the locked complex was formed only on the approach of DnaB helicase (the leading edge of the replication fork), and secondly, this locked complex was due to the base-flipping of C6 of ''Ter'' DNA into a cytosine-specific binding pocket on Tus. The approach of DnaB is essential to lock formation as strand separation is required before the C6 base can twist out of the helix. This C6 binds somewhere near the α4 helix, in or near the DNA-binding channel. | ||
His144 is a particularly important residue - it exists as its conjugate acid in the locked complex, forming hydrogen bonds with C6. Other residues - for example Phe140 and Gly149 - are also strictly conserved amongst different species' Tus protiens; many of the conserved residues among different ''Ter'' sites make base-specific contacts with Tus. | His144 is a particularly important residue - it exists as its conjugate acid in the locked complex, forming hydrogen bonds with C6. Other residues - for example Phe140 and Gly149 - are also strictly conserved amongst different species' Tus protiens; many of the conserved residues among different ''Ter'' sites make base-specific contacts with Tus. | ||
The locked Tus-''Ter'' complex is the most stable known monomeric DNa binding protein with a double-stranded sequence-specific recognition sequence - a half life of 550min has been reported (Mulcair, 2006). The formation of a large hydrogen-bond network is critical to sequence recognition and the stability of the twisted β-strands lying across the major groove. | The locked Tus-''Ter'' complex is the most stable known monomeric DNa binding protein with a double-stranded sequence-specific recognition sequence - a half life of 550min has been reported (Mulcair, 2006). The formation of a large hydrogen-bond network is critical to sequence recognition and the stability of the twisted β-strands lying across the major groove. | ||
<Structure load='1ECR' size='400' frame='true' align=' | |||
<Structure load='1ECR' size='400' frame='true' align='left' caption='Tus complexed with Ter DNA (Kamada ''et al'' 1996)' scene='Insert optional scene name here' /> | |||
<scene name='colorSTRUCTURE'>structure</scene> | <scene name='colorSTRUCTURE'>structure</scene> | ||
<Structure load='1F4K' size='400' frame='true' align=' | <Structure load='1F4K' size='400' frame='true' align='left' caption='RTP complexed with ''Ter''I B-site' (Wilce ''et al'' 2001)' scene='Insert optional scene name here' /> | ||
<scene name='colorSTRUCTURE'>structure</scene> | <scene name='colorSTRUCTURE'>structure</scene> | ||
== RTP: A homodimer responsible for Polar Arrest == | == RTP: A homodimer responsible for Polar Arrest == | ||
