A complete set of rate constants for a transporter’s catalytic cycle

The article by Lewis et al. (https://doi.org/10.1085/jgp.202413709) in this issue of JGP describes the use of single-molecule fluorescence polarization microscopy to obtain estimates of all the rate constants for transitions in the catalytic cycle of AdiC, a bacterial transporter for arginine and agmatine that has been believed to be a 1:1 exchanger.