User:David McDonald/Replication Termination Protein
From Proteopedia
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Revision as of 01:36, 23 May 2011
As with most bacteria, DNA replication of the circular chromosome of B. Subtilis occurs in a bi-directional fashion, starting from a common origin of replication (ori) and ending in the termination region, approximately 180o from the ori. The two replication forks are forced to meet in the termination region by replication termination proteins (RTPs) complexed to specific, unidirectional DNA termination sits (Ter sequences) termination region and arrest the action of the replication fork in a directional manner. That is, there are RTP:Ter complexes which stop replication in the clockwise and in the anti-clockwise direction. The clockwise replication fork is unaffected by the RTP:Ter complexes for the anti-clockwise fork and vice versa.
Contents |
DNA Replication in Bacteria
Structure
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contains 122 amino acid residues and is an example of a winged helix structure, in the α+β protein folding family, containing four α-helices and two β-strands[1]. The structure is named a "winged helix" due to the central , flanked by comprised of the two β-strands and the loops between them.
In a cell, RTP exists as a homodimer, where the monomer subunits are tightly associated through antiparallel coiled-coil interactions between the α4 helices to form the functional . This dimer is held together by between the two α4 helices.
For crystallographic studies, a mutant of RTP (C110S) was created to avoid possible unwanted disulfide bond formation. In this mutant, the Cysteine at position was changed to a Serine residue. It was shown that this did not result in a change in solution dimerisation or DNA binding functionality[2].
DNA Binding
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using
turns away from the dna
turns toward it
Replication Termination
Works Cited
1. Bussiere, DE, Bastia, D and White, SW. (1995)Crystal structure of replication terminator protein of B. subtilis at 2.6 Å. Cell. 80: 651-660.
2. J.P. Vivian, A.F. Hastings, I.G. Duggin, R.G. Wake, M.C.J. Wilce, and J.A. Wilce (2003) “The impact of single cysteine residue mutations on the replication terminator protein” Biochem. Biophys. Res. Commun. 310(4):1096-1103
