Role of tryptophan 54 in the binding of E. coli 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.