User:Nathan Harris/Tus: Difference between revisions
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Tus is divided into an <scene name='User:Nathan_Harris/Tus/Amino_domian/1'>amino domain</scene> and <scene name='User:Nathan_Harris/Tus/Carboxy_domain/1'>carboxy domain</scene> distinguished by two alpha helical regions and central β sheets combining to encompass a large central basic cleft. The <scene name='User:Nathan_Harris/Tus/Interdomain/2'>interdomain region</scene> consists of anti-parallel β strands and an <scene name='User:Nathan_Harris/Tus/L4/1'>extended L4 loop</scene> which connect the amino and carboxy domains. Within this interdomain region, the <scene name='User:Nathan_Harris/Tus/Bf/1'>βF</scene>, <scene name='User:Nathan_Harris/Tus/Bg/1'>βG</scene>, <scene name='User:Nathan_Harris/Tus/Bh/1'>βH</scene> and <scene name='User:Nathan_Harris/Tus/Bi/1'>βI</scene> strands are responsible for specific and non-specific recognition of ''Ter''. | Tus is divided into an <scene name='User:Nathan_Harris/Tus/Amino_domian/1'>amino domain</scene> and <scene name='User:Nathan_Harris/Tus/Carboxy_domain/1'>carboxy domain</scene> distinguished by two alpha helical regions and central β sheets combining to encompass a large central basic cleft. The <scene name='User:Nathan_Harris/Tus/Interdomain/2'>interdomain region</scene> consists of anti-parallel β strands and an <scene name='User:Nathan_Harris/Tus/L4/1'>extended L4 loop</scene> which connect the amino and carboxy domains. Within this interdomain region, the <scene name='User:Nathan_Harris/Tus/Bf/1'>βF</scene>, <scene name='User:Nathan_Harris/Tus/Bg/1'>βG</scene>, <scene name='User:Nathan_Harris/Tus/Bh/1'>βH</scene> and <scene name='User:Nathan_Harris/Tus/Bi/1'>βI</scene> strands are responsible for specific and non-specific recognition of ''Ter''. | ||
The amino domain consists of three amphipathic alpha helices forming an anti-parallel bundle roughly parallel to ''Ter'', a sandwich of anti-parallel β sheets and three loops. The major groove and minor groove are clamped by two alpha helices (<scene name='User:Nathan_Harris/Tus/A4/1'>αIV</scene> and <scene name='User:Nathan_Harris/Tus/A5/1'>αV</scene>) which also contribute to the hydrophobic core of the protein. Within the β sandwich, <scene name='User:Nathan_Harris/Tus/Bcadke/1'>βCADKE</scene> contacts the alpha helical region, whereas <scene name='User:Nathan_Harris/Tus/Blfij/1'>βLFIJ</scene> is associated with DNA binding. Furthermore, the extended L4 loop is also involved in contacts to the minor groove. | The amino domain consists of three amphipathic alpha helices forming an anti-parallel bundle roughly parallel to ''Ter'', a sandwich of anti-parallel β sheets and three loops. The major groove and minor groove are clamped by two alpha helices (<scene name='User:Nathan_Harris/Tus/A4/1'>αIV</scene> and <scene name='User:Nathan_Harris/Tus/A5/1'>αV</scene>) which also contribute to the hydrophobic core of the protein. Within the β sandwich, <scene name='User:Nathan_Harris/Tus/Bcadke/1'>βCADKE</scene> contacts the alpha helical region, whereas <scene name='User:Nathan_Harris/Tus/Blfij/1'>βLFIJ</scene> is associated with DNA binding. Furthermore, the extended L4 loop is also involved in contacts to the minor groove. | ||
The carboxy domain consists of a hydrophobic core stabilised by alpha helices and β strands (βGHNO). The L3 loop is responsible for connecting helices αVI and αVII and also contacts the minor groove of DNA. | The carboxy domain consists of a hydrophobic core stabilised by alpha helices and β strands (βGHNO). The <scene name='User:Nathan_Harris/Tus/L3/1'>L3 loop</scene> is responsible for connecting helices <scene name='User:Nathan_Harris/Tus/A6/1'>αVI</scene> and <scene name='User:Nathan_Harris/Tus/A7/1'>αVII</scene> and also contacts the minor groove of DNA. | ||
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It has been suggested that the affinity of Tus for ''Ter'' may contribute to the polar arrest of replication in ''E. coli'' demonstrated by a direct | It has been suggested that the affinity of Tus for ''Ter'' may contribute to the polar arrest of replication in ''E. coli'' demonstrated by a direct | ||
correlation between the affinity and replication termination. | correlation between the affinity and replication termination. | ||
Investigations of the affinity of Tus for partially unwound ''Ter'' DNA have provided crystal structures of Tus bound to ''Ter'' unwound at the C6 of ''Ter''. | Investigations of the affinity of Tus for partially unwound ''Ter'' DNA have provided crystal structures of Tus bound to ''Ter'' unwound at the <scene name='User:Nathan_Harris/Tus/C6/1'>C6</scene> of ''Ter''. | ||
These crystal structures show the C6 of ''Ter'' flipped up into a hydrophobic pocket | These crystal structures show the C6 of ''Ter'' flipped up into a <scene name='User:Nathan_Harris/Tus/Pocket/1'>hydrophobic pocket</scene> of Tus forming a so called locked complex. | ||
This locking results in a dramatic increase in the affinity of Tus for ''Ter''. In contrast, the progressive unwinding of ''Ter'' from the permissive face | This locking results in a dramatic increase in the affinity of Tus for ''Ter''. In contrast, the progressive unwinding of ''Ter'' from the permissive face | ||
results in dissociation of Tus from ''Ter''. It is interesting to note that this C6 is conserved amongst all ''Ter'' sequences, further demonstrating the | results in dissociation of Tus from ''Ter''. It is interesting to note that this C6 is conserved amongst all ''Ter'' sequences, further demonstrating the | ||