Sandbox20: Difference between revisions

[[Image:Tus 1 labelled helices.jpg | thumb | upright=1.6| left| Secondary structures of the Tus protein.]]

The structure of the Tus protein was determined in complex with TerA by Kamada et al., and shown to be a previously undescribed backbone conformation (<scene name='Sandbox20/Tus/2'>original image</scene>.). It is divided into two domains (amino and carboxy), in which α-helical regions of each are spanned by a central β-sandwich which contacts 13 bp of DNA duplex (#Indicate domains). Three helices within the amino domain (αI αII, αIII) form an antiparallel bundle aligned parallel to the DNA (#Helix bundle). Another two helices (αIV, αV) clamp the DNA phosphate backbone at the non-permissive end, and forms the cytosine-specific pocket containing the crucial residues for anti-helicase activity (#Phosphate clamp). The main DNA-binding domain however is the exposed side of the double β sheet layer which provides several base-specific interactions. This lies within the major groove and causes a conformational change in the DNA involving a deepening of the major groove, and an expansion of the minor one (#Sheet position).