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. 1987 Aug;6(8):2493–2498. doi: 10.1002/j.1460-2075.1987.tb02531.x

The accessibility of DNA to dimethylsulfate in complexes with recA protein.

E Di Capua 1, B Müller 1
PMCID: PMC553659  PMID: 3665884

Abstract

recA protein coats DNA co-operatively to form filaments approximately 100 A thick, which in the presence of ATP, and more stably so in the presence of the non-hydrolyzable analog ATP gamma S, have a helical appearance with a deep cleft in the protein coat. This protein helix follows the DNA helix, to which it imparts a new helicity of 18.5 bp per turn of 97 A pitch. Here we test the accessibility of the DNA in the complex to modification by dimethylsulfate, and find that the complexed DNA is approximately 2-fold more reactive on the major groove side than it was in B-DNA (methylation of guanine N7), while it is protected approximately 2-fold on the minor groove side (methylation of adenine N3), suggesting that the protein coats the DNA along the minor groove. Furthermore, N3 of cytosine, a residue involved in base pairing, is found exposed in complexes with single strands as it is in naked single-stranded DNA, while it remains inaccessible in complexes with double strands, suggesting that the latter is not melted at this stage of the strand exchange reaction.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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