User:Nathan Harris/Tus: Difference between revisions

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=='''Biological role'''==

Multiple ''Ter'' sites (''TerA''- ''TerJ'') are located in regions destined for replication termination in ''E. coli''. Tus binds specifically to these 23bp ''Ter'' sites forming a Tus-''Ter'' complex . This complex allows for the blocking of an approaching replication fork in one direction, the non-permissive face, but not from the other direction, the permissive face. The ability to halt the replication machinery at the non-permissive face is thought to involve the inhibition of DnaB Helicase, preventing it from unwinding DNA. DnaB inhibition has been proposed to occur either through protein-protein interactions between Tus and DnaB, or by a physical block provided by Protein-DNA interactions i.e. the Tus-''Ter'' complex <ref name = "Kamada"> Kamada, K., Horiuchi, T., Ohsumi, K., Shimamoto, N. and Morikawa, K. (1996) Structure of a replication-terminator protein complexed with DNA. Nature 383 (6681): 598-603.</ref>. Recent models suggest a potentially combination of these two mechanisms <ref name = "Kaplan"> Kaplan, D. L. and Bastia, D. (2009) Mechanisms of polar arrest of replication fork. Molecular biology, 72 (2): 279-285.</ref>. Evolution of this termination system has allowed for efficient replication by ''E. coli'' as it prevents any over expenditure of energy or time. Different replication proteins have been found in other model organisms, such as RTP in ''Bacillus subtilis''. Despite similar biological roles of RTP and Tus they have significantly different structures.

Multiple ''Ter'' sites (''TerA''- ''TerJ'') are located in regions destined for replication termination in ''E. coli''. Tus binds specifically to these 23bp ''Ter'' sites forming a Tus-''Ter'' complex . This complex allows for the blocking of an approaching replication fork in one direction, the non-permissive face, but not from the other direction, the permissive face. The ability to halt the replication machinery at the non-permissive face is thought to involve the inhibition of DnaB Helicase, preventing it from unwinding DNA. DnaB inhibition has been proposed to occur either through protein-protein interactions between Tus and DnaB, or by a physical block provided by Protein-DNA interactions i.e. the Tus-''Ter'' complex <ref name = "Kamada"> Kamada, K., Horiuchi, T., Ohsumi, K., Shimamoto, N. and Morikawa, K. (1996) Structure of a replication-terminator protein complexed with DNA. Nature 383 (6681): 598-603.</ref>. Recent models suggest a potentially combination of these two mechanisms <ref name = "Kaplan"> Kaplan, D. L. and Bastia, D. (2009) Mechanisms of polar arrest of replication fork. Molecular biology, 72 (2): 279-285.</ref>. Evolution of this termination system has allowed for efficient replication by ''E. coli'' as it prevents any over expenditure of energy or time. Different replication proteins have been found in other model organisms, such as RTP in ''Bacillus subtilis''. Despite similar biological roles of RTP and Tus they have significantly different structures <ref name = "Kaplan" />.

=='''Ter sites'''==

The Tus protein binds as a monomer through several direct and indirect contacts to conserved ''Ter'' sites. Ter sites are signified by 23 bp of consensus sequences which maintain a highly conserved C6 and 13 bp core region that interacts with Tus. Additionally, ''Ter'' sites are arranged in groups of five located opposite to the origin of replication. Within each group the ''Ter'' sites have a coordinated polarity of termination.

The Tus protein binds as a monomer through several direct and indirect contacts to conserved ''Ter'' sites. Ter sites are signified by 23 bp of consensus sequences which maintain a highly conserved C6 and 13 bp core region that interacts with Tus. Additionally, ''Ter'' sites are arranged in groups of five located opposite to the origin of replication. Within each group the ''Ter'' sites have a coordinated polarity of termination <ref name = "Neylon" />.

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 =='''Biological role'''==
-Multiple ''Ter'' sites (''TerA''- ''TerJ'') are located in regions destined for replication termination in ''E. coli''. Tus binds specifically to these 23bp ''Ter'' sites forming a Tus-''Ter'' complex . This complex allows for the blocking of an approaching replication fork in one direction, the non-permissive face, but not from the other direction, the permissive face.  The ability to halt the replication machinery at the non-permissive face is thought to involve the inhibition of DnaB Helicase, preventing it from unwinding DNA. DnaB inhibition has been proposed to occur either through protein-protein interactions between Tus and DnaB, or by a physical block provided by Protein-DNA interactions i.e. the Tus-''Ter'' complex <ref name = "Kamada"> Kamada, K., Horiuchi, T., Ohsumi, K., Shimamoto, N. and Morikawa, K.  (1996) Structure of a replication-terminator protein complexed with DNA.  Nature 383 (6681): 598-603.</ref>.  Recent models suggest a potentially combination of these two mechanisms <ref name = "Kaplan"> Kaplan, D. L. and Bastia, D.  (2009) Mechanisms of polar arrest of replication fork.  Molecular biology, 72 (2): 279-285.</ref>. Evolution of this termination system has allowed for efficient replication by ''E. coli'' as it prevents any over expenditure of energy or time.  Different replication proteins have been found in other model organisms, such as RTP in ''Bacillus subtilis''.  Despite similar biological roles of RTP and Tus they have significantly different structures.
+Multiple ''Ter'' sites (''TerA''- ''TerJ'') are located in regions destined for replication termination in ''E. coli''. Tus binds specifically to these 23bp ''Ter'' sites forming a Tus-''Ter'' complex . This complex allows for the blocking of an approaching replication fork in one direction, the non-permissive face, but not from the other direction, the permissive face.  The ability to halt the replication machinery at the non-permissive face is thought to involve the inhibition of DnaB Helicase, preventing it from unwinding DNA. DnaB inhibition has been proposed to occur either through protein-protein interactions between Tus and DnaB, or by a physical block provided by Protein-DNA interactions i.e. the Tus-''Ter'' complex <ref name = "Kamada"> Kamada, K., Horiuchi, T., Ohsumi, K., Shimamoto, N. and Morikawa, K.  (1996) Structure of a replication-terminator protein complexed with DNA.  Nature 383 (6681): 598-603.</ref>.  Recent models suggest a potentially combination of these two mechanisms <ref name = "Kaplan"> Kaplan, D. L. and Bastia, D.  (2009) Mechanisms of polar arrest of replication fork.  Molecular biology, 72 (2): 279-285.</ref>. Evolution of this termination system has allowed for efficient replication by ''E. coli'' as it prevents any over expenditure of energy or time.  Different replication proteins have been found in other model organisms, such as RTP in ''Bacillus subtilis''.  Despite similar biological roles of RTP and Tus they have significantly different structures <ref name = "Kaplan" />.
 =='''Ter sites'''==
-The Tus protein binds as a monomer through several direct and indirect contacts to conserved ''Ter'' sites.  Ter sites are signified by 23 bp of consensus sequences which maintain a highly conserved C6 and 13 bp core region that interacts with Tus.  Additionally, ''Ter'' sites are arranged in groups of five located opposite to the origin of replication.  Within each group the ''Ter'' sites have a coordinated polarity of termination.
+The Tus protein binds as a monomer through several direct and indirect contacts to conserved ''Ter'' sites.  Ter sites are signified by 23 bp of consensus sequences which maintain a highly conserved C6 and 13 bp core region that interacts with Tus.  Additionally, ''Ter'' sites are arranged in groups of five located opposite to the origin of replication.  Within each group the ''Ter'' sites have a coordinated polarity of termination <ref name = "Neylon" />.