A perspective on conformational control of electron transfer in nitric oxide synthases

•The catalytic mechanism of NOS and related diflavin oxidoreductase has been extensively studied.•Numerous studies have shown that NOS electron transfer chemistry is 'gated' by protein domain motion.•Time-resolved fluorescence spectroscopy is a valuable tool for the study of NOS and related diflavin oxidoreductase dynamics.

This perspective reviews single molecule and ensemble fluorescence spectroscopy studies of the three tissue specific nitric oxide synthase (NOS) isoenzymes and the related diflavin oxidoreductase cytochrome P450 reductase. The focus is on the role of protein dynamics and the protein conformational landscape and we discuss how recent fluorescence-based studies have helped in illustrating how the nature of the NOS conformational landscape relates to enzyme turnover and catalysis.