Comparing the temperature dependence of FMN to heme electron transfer in full length and truncated inducible nitric oxide synthase proteins

► The FMN-heme IET kinetics in full length and truncated oxygenase/FMN construct iNOS proteins were determined at 283-304 K. ► This is the first study of temperature dependence of the NOS IET kinetics. ► Eyring equation was used to analyze the temperature dependence data. ► The magnitude of activation entropy for the IET in the oxygenase/FMN construct is only one-fifth of that for the holoenzyme. ► The results indicate that the FMN domain in the holoenzyme needs to sample more conformations before the IET takes place.