RecA Protein Promotes Strand Exchange with DNA Substrates Containing Isoguanine and 5-Methyl Isocytosine

The Escherichia coli RecA protein pairs homologous DNA molecules and promotes DNA strand exchange in vitro. We have examined DNA strand exchange between a 70 nucleotide ssDNA fragment and a 40 bp duplex, in which all G and C residues (at 18 positions distributed throughout the 40 bp exchanged region...

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Bibliographic Details
Published in:Biochemistry (Easton) 2000-08, Vol.39 (33), p.10177-10188
Main Authors: Rice, Kevin P, Chaput, John C, Cox, Michael M, Switzer, Christopher
Format: Article
Language:English
Subjects:
5-Methyl isocytosine
5-Methylcytosine - analogs & derivatives
Cytosine - analogs & derivatives
DNA - metabolism
DNA Replication
DNA, Single-Stranded - metabolism
DNA-Binding Proteins - metabolism
Escherichia coli
Guanine
Isoguanine
Models, Chemical
Models, Molecular
Nucleic Acid Conformation
Oligodeoxyribonucleotides
Rec A Recombinases - metabolism
RecA protein
Recombination, Genetic
Substrate Specificity
Thermodynamics
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Summary:The Escherichia coli RecA protein pairs homologous DNA molecules and promotes DNA strand exchange in vitro. We have examined DNA strand exchange between a 70 nucleotide ssDNA fragment and a 40 bp duplex, in which all G and C residues (at 18 positions distributed throughout the 40 bp exchanged region) were replaced with the nonstandard nucleosides 2‘-deoxyisoguanosine (iG) and 2‘-deoxy-5-methylisocytidine (MiC), respectively. We demonstrate that the nonstandard oligonucleotides are substrates for the RecA protein, permitting DNA strand exchange in vitro at a rate and efficiency comparable to exchange with normal DNA substrates. This observation provides an expanded experimental basis for discussions of potential roles for iG and MiC in a genetic code. Experiments of this type also provide another avenue for exploring RecA-facilitated DNA pairing mechanisms.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi0003339