Role of tryptophan 54 in the binding of <i>E. coli</i> single‐stranded DNA‐binding protein to single‐stranded polynucleotides

Abstract

Fluorescence and optical detection of triplet state magnetic resonance spectroscopy have been employed to study the complexes formed by single-stranded polynucleotides with both E. coli single-stranded DNA-binding protein and an E. coli ssb gene product in which Trp-54 is replaced by phenylalanine using site specific oligonucleotide mutagenesis. Our results strongly suggest the involvement of Trp-54 in stabilizing the protein-nucleic acid complexes via stacking interactions of the aromatic residue with the nucleotide bases.