Structural change of a cofactor binding site of flavoprotein detected by single-protein fluorescence spectroscopy at 1.5 k.

The visible fluorescence spectrum of single flavoprotein at a temperature of 1.5 K has been measured by one-photon excitation. The flavoprotein studied was a photoswitchable enzyme, photoactivated adenylyl cyclase. The time course of the spectrum revealed a structural change occurring at a rate of 10(-3)  s(-1) around hydrogen bonds at the flavin cofactor binding site.