eLife Assessment
This useful work employs transition-metal FRET (tmFRET) to study the cyclic nucleotide binding domain (CNBD) of a bacterial ion channel. The authors employ lifetime measurements of fluorescence to extend their own prior study and observe distance changes within the CNBD domains of a full-length channel; they base these measurements on changes in lifetimes due to tmFRET between a metal at an introduced chelator site and a fluorescent non-canonical amino acid at another site within the channel sequence. This allows the authors to show that coupling of the CNBDs to the rest of the channel stabilizes the CNBDs in their active state relative to an isolated CNBD construct. The data are compelling and of high quality, and support the authors' conclusions.
