Sandbox20: Difference between revisions
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The displacement of a <scene name='Sandbox20/Tus/13'>single conserved cytosine</scene> nucleotide from the double helix determines the polarity of fork arrest.<ref>PMID: 16814717</ref> This is located at the edge of the non-permissive face, and defines the point at which helicase activity is halted. Upon interaction with Tus the cyotsine is no longer base-paired, and is instead associated with residues within a well-defined recognition pocket.<ref>PMID: 16814717</ref> The specific interactions which stabilise this are shown in this <scene name='Sandbox20/Tus/9'>model</scene>. | The displacement of a <scene name='Sandbox20/Tus/13'>single conserved cytosine</scene> nucleotide from the double helix determines the polarity of fork arrest.<ref>PMID: 16814717</ref> This is located at the edge of the non-permissive face, and defines the point at which helicase activity is halted. Upon interaction with Tus the cyotsine is no longer base-paired, and is instead associated with residues within a well-defined recognition pocket.<ref>PMID: 16814717</ref> The specific interactions which stabilise this are shown in this <scene name='Sandbox20/Tus/9'>model</scene>. | ||
Before the structure of the Tus-Ter complex was determined, mutation of Glu49 was shown to eliminate anti-helicase activity without affecting DNA binding.<ref>PMID: 11493686</ref> This could not be explained by the [[1ecr|original crystal structure]] as it is not located close enough to make direct contact with the conserved cytosine.<ref | Before the structure of the Tus-Ter complex was determined, mutation of Glu49 was shown to eliminate anti-helicase activity without affecting DNA binding.<ref>PMID: 11493686</ref> This could not be explained by the [[1ecr|original crystal structure]] as it is not located close enough to make direct contact with the conserved cytosine.<ref>PMID: 11493686</ref> However, the [[2ewj|more recent structure]] revealed that this is due the water-mediated hydrogen bond formed between it and the adenine residue adjacent to cytosine.<ref>PMID: 16814717</ref> It is therefore likely, that the interaction is necessary to compensate for the disrupted H-bonding in the nucleotide adjacent to the displaced cytosine, as shown in this <scene name='Sandbox20/Tus/18'>model</scene>. | ||
Index of Tus scenes: [1] <scene name='Sandbox20/Tus/2'>Original</scene>, [2] <scene name='Sandbox20/Tus/19'>DNA binding</scene>, [3] <scene name='Sandbox20/Tus/13'>Conserved cytosine</scene>, [4] <scene name='Sandbox20/Tus/9'>Cytosine displacement</scene>, [5] <scene name='Sandbox20/Tus/18'>E49 hydrogen bond</scene>. | Index of Tus scenes: [1] <scene name='Sandbox20/Tus/2'>Original</scene>, [2] <scene name='Sandbox20/Tus/19'>DNA binding</scene>, [3] <scene name='Sandbox20/Tus/13'>Conserved cytosine</scene>, [4] <scene name='Sandbox20/Tus/9'>Cytosine displacement</scene>, [5] <scene name='Sandbox20/Tus/18'>E49 hydrogen bond</scene>. | ||