Recombinant Gaussia luciferase with a reactive cysteine residue for chemical conjugation: Expression, purification and its application for bioluminescent immunoassays

► The mutated recombinant Gaussia luciferase having a reactive cysteine residue (hgGLase) was purified from E. coli cells. ► Biotinylated hgGLase (Biotin-hgGLase) and fluorescein-labeled hgGLase were prepared by chemical conjugation. ► We applied Biotin-hgGLase to bioluminescent immunoassay. ► The sensitivity of Biotin-hgGLase was similar to that of other detection systems using the biotinylated reporter proteins.