Binding of recA protein to single- and double-stranded polynucleotides occurs without involvement of its aromatic residues in stacking interactions with nucleotide bases.
Phosphorescence and optically detected triplet state magnetic resonance (ODMR) spectroscopy studies of recA protein and its complexes with poly(5-HgU) and poly(dA-5BrdU) show that the two tryptophan residues are not involved in stacking interactions with the nucleotide bases of either single- or double-stranded polynucleotides. Solvent conditions which induce preferential binding to single-stranded ligands result in a shortening of the tyrosine phosphorescence lifetime, which is further reduced upon binding to poly(5-HgU). This suggests a change in the global conformation or self-aggregation state of the protein. Binding to poly(dA-5BrdU) induces small changes in the tryptophan zero field splittings of recA, but significant changes on those of 5BrdU, which are consistent with recA binding to the minor groove of the polynucleotide.
Khamis
M I
MI
Department of Chemistry, University of California, Davis 95616.
Casas-Finet
J R
JR
Maki
A H
AH
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004247:DNA; D004277:DNA, Single-Stranded; D008163:Luminescent Measurements; D009682:Magnetic Resonance Spectroscopy; D010649:Phenylalanine; D011938:Rec A Recombinases; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D014443:Tyrosine
D004277:DNA, Single-Stranded; D014443:Tyrosine; D010649:Phenylalanine; D004247:DNA; D011938:Rec A Recombinases