The P1 phage replication protein RepA contacts an otherwise inaccessible thymine N3 proton by DNA distortion or base flipping
AUTOR(ES)
Lyakhov, Ilya G.
FONTE
Oxford University Press
RESUMO
The RepA protein from bacteriophage P1 binds DNA to initiate replication. RepA covers one face of the DNA and the binding site has a completely conserved T that directly faces RepA from the minor groove at position +7. Although all four bases can be distinguished through contacts in the major groove of B-form DNA, contacts in the minor groove cannot easily distinguish between A and T bases. Therefore the 100% conservation at this position cannot be accounted for by direct contacts approaching into the minor groove of B-form DNA. RepA binding sites with modified base pairs at position +7 were used to investigate contacts with RepA. The data show that RepA contacts the N3 proton of T at position +7 and that the T=A hydrogen bonds are already broken in the DNA before RepA binds. To accommodate the N3 proton contact the T+7 /A+7′ base pair must be distorted. One possibility is that T+7 is flipped out of the helix. The energetics of the contact allows RepA to distinguish between all four bases, accounting for the observed high sequence conservation. After protein binding, base pair distortion or base flipping could initiate DNA melting as the second step in DNA replication.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=96704Documentos Relacionados
- P1 plasmid replication: multiple functions of RepA protein at the origin.
- Replication of mini-P1 plasmid DNA in vitro requires two initiation proteins, encoded by the repA gene of phage P1 and the dnaA gene of Escherichia coli.
- Analysis of functional domains of Rts1 RepA by means of a series of hybrid proteins with P1 RepA.
- Monomers and dimers of the RepA protein in plasmid pSC101 replication: domains in RepA.
- Regulatory interactions between RepA, an essential replication protein, and the DNA repeats of RepFIB from plasmid P307.