a, Immunoblot for MBP-Hem25p, MBP-SLC25A38, and MBP-Yhm2p in E. coli membranes preparations. b, Steady-state kinetics of [1-14C]-IPP uptake in cells expressing MBP-Hem25p or the empty vector. Initial rates (nmol/min) values represent the mean ± SD of three biologically independent samples. c, Time course of 50 μM [phenyl-14C6]-4-HB uptake by E. coli cells expressing the Pseudomonas putida PcaK or the empty vector (*p = 0.0002, **p = 0.0042, ***p = 0.0006, ****p = 0.0011 empty vector vs pcaK, mean ± SD, n = 3 biologically independent samples, two-sided Student’s t-test). Source numerical data and unprocessed blots are available in source data.