Mutant firefly luciferases with improved specific activity and dATP discrimination constructed by yeast cell surface engineering

Pyrosequencing system utilizing luciferase is one of the next-generation DNA sequencing systems. However, there is a crucial problem with the current pyrosequencing system: luciferase cannot discriminate between ATP and dATP completely, and dATP alpha S must be used as the dATP analogue. dATP alpha S is expensive and has low activity for the enzyme. If luciferase can clearly recognize the difference between ATP and dATP, dATP could be used instead of the expensive dATP alpha S in the pyrosequencing system. We attempted to prepare a novel luciferase with improved specific activity and dATP discrimination with the molecular display method. First, we selected two amino acid residues, Ser440 and Ser456, as target residues for mutation from the whole sequence of Photinus pyralis luciferase; we comprehensively mutated these two amino acids. A mutant luciferase library was constructed using yeast cell surface engineering. Through three step-wide screenings with individual conditions, we easily and speedily isolated three candidate mutants from 1,152 candidates and analyzed the properties of these mutants. Consequently, we succeeded in obtaining interesting mutant luciferases with improved specific activity and dATP discrimination more conveniently than with other methods.