A cysteine-free firefly luciferase retains luminescence activity

A mutant of Photinus pyralis luciferase in which all four native cysteine r esidues are converted to serines retains about 10% of wild-type activity. T his mutant should prove useful as a starting point for the introduction of biophysical probes of conformational changes associated with enzyme functio n. The activities of the cysteine-free mutant and others in which two or th ree cysteines are converted to serines suggest, however, that small chemica l changes can have substantial and interdependent effects on bioluminescenc e. The introduction of probes should therefore be approached cautiously. (C ) 2000 Academic Press.