Introduction of a unique tryptophan residue into various positions of Bacillus licheniformis DnaK

► Effects of single-tryptophan-incorporated mutations on Bacillus licheniformis DnaK were investigated. ► The individual replacement of five Phe residues of the molecular chaperone with Trp does cause a significant perturbation of the protein's functionality. ► The quenching characteristics of these variants can be used to probe protein conformation alteration that affects its tryptophan accessibility.