The L2 loop peptide of RecA stiffens and restricts base motions of single-stranded DNA similar to the intact protein.
The L2 loop in the RecA protein is the catalytic center for DNA strand exchange. Here we investigate the DNA binding properties of the L2 loop peptide using optical spectroscopy with polarized light. Both fluorescence intensity and anisotropy of an etheno-modified poly(dA) increase upon peptide binding, indicate that the base motions of single-stranded DNA are restricted in the complex. In agreement with this conclusion, the peptide-poly(dT) complex exhibits a significant linear dichroism signal. The peptide is also found to modify the structure of double-stranded DNA, but does not denature it. It is inferred that strand separation may not be required for the formation of a joint molecule.
Selmane
T
T
Unité Mixte de Recherche 216, Institut Curie and CNRS, Orsay, France.
Wittung-Stafshede
P
P
Maraboeuf
F
F
Voloshin
O N
ON
Nordén
B
B
Camerini-Otero
D R
DR
Takahashi
M
M
D020029:Base Pairing / Q000187:drug effects; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011938:Rec A Recombinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011995:Recombination, Genetic
D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D010455:Peptides; D011938:Rec A Recombinases