Firefly luciferase has two nucleotide binding sites: effect of nucleoside monophosphate and CoA on the light-emission spectra

A laboratory-made spectroluminometer was used to analyse the light emitted by firefly (Photinus pyralis) luciferase reacting with several nucleotide d erivatives. The analysis of the light emission in the presence of ATP or dA TP provides some evidence that the enzyme has two nucleotide binding sites, each one leading to the formation of a complex emitting mainly at 575 m (A TP) or 610 nm (dATP). AMP is able to displace dATP from the second site (61 0 nm) to the first one. Photoaffinity labelling of the second site by 8-azi do-AMP gives similar results. The amplification effect of CoA and acetyl-Co A is also reconsidered according to this model.