Fig. 2

Characterization of the components of the system. a Molecular and kinetic properties of the enzymes; K_eq was calculated as in Fig. 1c. The K_M values of a given substrate were determined under conditions of excess of the other substrate. The number of molecules per vesicle was calculated from the internal concentration of the enzymes and the average size of the vesicles, for 400 nm (left column) and 200 nm (right column) extruded vesicles. Kinetic parameters of ArcB are given for the back reaction. The kinetic parameters of ArcD2 were estimated from measurements in cells⁴⁸, assuming that ArcD2 constitutes 1% of membrane protein; the data for OpuA are from ref. ⁴⁰. b Distribution of the radius of lipid vesicles extruded through a 400 nm (blue bars) and 200 nm (black bars) polycarbonate filter as estimated from CryoTEM micrographs (Supplementary Fig. 1). The diameter of 2090 vesicles (400 nm filter) and 2092 vesicles (200 nm filter) were measured using ImageJ. c Distribution of the internal volume, based on the distribution of radii, assuming that all vesicles are spherical. d Kinetics of arginine uptake in proteoliposomes with 1 mM (blue circles) and 0.1 mM (black squares) ornithine on the inside (protocol B2); ¹⁴C-arginine concentration of 10 µM. Inset: influence of a membrane potential (ΔΨ) on arginine uptake with 1 mM ornithine on the inside. Data from replicate experiments (n = 2) are shown, error bars indicate standard deviation. e Kinetics of arginine uptake in proteoliposomes with 10 mM (blue circles) and 1 mM (black squares) citrulline on the inside (protocol B2); ¹⁴C-arginine concentration of 10 µM. Inset: influence of a membrane potential (ΔΨ) on arginine uptake with 10 mM citrulline on the inside (n = 2). Source data of are provided as a Source Data file