RTP and Tus: Difference between revisions
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Looking at the structures of these two proteins, it is not immediately obvious that they would perfom the same function; to arrest the progression of the replication fork along the bacterial chromosome at specific sites (''Ter'' sites). Furthermore, this arrest-mechanism functions in a polar manner in both organisms, which is perhaps surprising considering the symmetrical characteristics of both proteins.<ref>Wake, RG and King, GF (1997) A tale of two terminators: crystal structures sharpen the debate on DNA replication fork arrest mechanisms. ''Structure'' 5: 1-5.</ref> | Looking at the structures of these two proteins, it is not immediately obvious that they would perfom the same function; to arrest the progression of the replication fork along the bacterial chromosome at specific sites (''Ter'' sites). Furthermore, this arrest-mechanism functions in a polar manner in both organisms, which is perhaps surprising considering the symmetrical characteristics of both proteins.<ref>Wake, RG and King, GF (1997) A tale of two terminators: crystal structures sharpen the debate on DNA replication fork arrest mechanisms. ''Structure'' 5: 1-5.</ref> | ||
[[Image:Replication_fork.jpg|300px|right|thumb| Schematic representation of ''Ter'' sites in ''B. subtilis'' and ''E. coli''. ]] | |||
== The Replication Fork and Polar Arrest == | == The Replication Fork and Polar Arrest == | ||
DNA replication of circular bacterial chromosomes occurs using two replication forks that originate from a single location (''oriC'') and move in opposite directions around the chromosome. In ''E. coli'', ''B. subtilis'', and other bacteria and archaea, these replication forks are halted by interactions with terminator proteins bound to DNA sites known as "Terminator sites", or''Ter'' sites. The termination of the replication fork is dependent on the direction of approach to these ''Ter'' sites: if the replication fork approaches from the permissive face replication will continue; however, if the replication fork approaches from the non-permissive face the fork will be arrested and DNA replication will cease at that point. While it is possible for these organisms to function without this type of replication-arrest mechanism, the conservation of this system across species indicates some form of evolutionary benefit. | DNA replication of circular bacterial chromosomes occurs using two replication forks that originate from a single location (''oriC'') and move in opposite directions around the chromosome. In ''E. coli'', ''B. subtilis'', and other bacteria and archaea, these replication forks are halted by interactions with terminator proteins bound to DNA sites known as "Terminator sites", or''Ter'' sites. The termination of the replication fork is dependent on the direction of approach to these ''Ter'' sites: if the replication fork approaches from the permissive face replication will continue; however, if the replication fork approaches from the non-permissive face the fork will be arrested and DNA replication will cease at that point. While it is possible for these organisms to function without this type of replication-arrest mechanism, the conservation of this system across species indicates some form of evolutionary benefit. | ||
