Table 1.

Stoichiometry of interactions of HsRad51 with 83-mer oligonucleotides

Assay	% of maximal reaction at protein/DNA ratio
	1:2	1:3	1:6
Binding to ssDNA
Filter assay	100	92	56
Fluorescence assay	100	95	78
Strand exchange
Gel assay	100	96	32
Binding to dsDNA
Filter assay	100	98	44
ATPase activity with ssDNA	100	84	51

Reaction conditions were as described in the text. Binding reactions were carried out at 37°C for 4 min. The same stoichiometry was observed when the strand exchange assay was done with 33-mer or 83-mer oligonucleotides. The strand exchange assay was carried out for 60 min and reached a yield of 60% in the case the 83-mer substrates. Protein/DNA ratio refers to moles of HsRad51 per mole of nucleotide residue, or, in the case of binding to duplex oligonucleotide, mole of base pairs. ATPase was assayed as described (25).