Journal: iScience
Article Title: Lipochaperoning folding of water-soluble functional membrane protein in genetically and biosynthetically tuned Escherichia coli
doi: 10.1016/j.isci.2026.115237
Figure Lengend Snippet: Soluble LacY permease can be reconstituted into liposomes that catalyze lactose active transport monitored by [ 14 C]lactose uptake in response to a membrane potential induced by valinomycin (interior negative) The soluble LacY was purified and reconstituted into proteoliposomes as described under and legend to figure (A). A schematic representation of the LacY activity assay is shown. Dilution of liposomes containing K + into Na + in the presence of valinomycin generates a positive outward membrane potential (ΔΨ) (B). To measure membrane potential-driven uphill transport, 10 μL of proteoliposomes were diluted into NaP i (pH 7.5) containing 0.1 mM [ 14 C] lactose and 10 μm valinomycin. At the times indicated, the reactions were quenched and counted as described in . Uphill transport of lactose is driven by DY (interior negative) when [K + ]in > [K + ]out at the time of dilution. Bottom set of time points represents dilution into 50 mM KP i containing 10 μm nigericin (negative control), which was used to dissipate the membrane potential and perform measurements with de-energized proteoliposomes. The radioactivity taken up by the proteoliposomes was converted to lactose concentration and normalized to the amount of LacY in the sample. A background value was determined by assaying protein-free liposomes lacking LacY and was subtracted from all measurements. All incubations were at 30°C. Average results representative of three experiments are shown. Data are represented as mean ± SEM.
Article Snippet: [ 14 C] Lactose , Moravek , MC1466.
Techniques: Liposomes, Membrane, Purification, Activity Assay, Negative Control, Radioactivity, Concentration Assay
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![Soluble LacY permease can be reconstituted into liposomes that catalyze lactose active transport monitored by [ 14 C]lactose uptake in response to a membrane potential induced by valinomycin (interior negative) The soluble LacY was purified and reconstituted into proteoliposomes as described under and legend to figure (A). A schematic representation of the LacY activity assay is shown. Dilution of liposomes containing K + into Na + in the presence of valinomycin generates a positive outward membrane potential (ΔΨ) (B). To measure membrane potential-driven uphill transport, 10 μL of proteoliposomes were diluted into NaP i (pH 7.5) containing 0.1 mM [ 14 C] lactose and 10 μm valinomycin. At the times indicated, the reactions were quenched and counted as described in . Uphill transport of lactose is driven by DY (interior negative) when [K + ]in > [K + ]out at the time of dilution. Bottom set of time points represents dilution into 50 mM KP i containing 10 μm nigericin (negative control), which was used to dissipate the membrane potential and perform measurements with de-energized proteoliposomes. The radioactivity taken up by the proteoliposomes was converted to lactose concentration and normalized to the amount of LacY in the sample. A background value was determined by assaying protein-free liposomes lacking LacY and was subtracted from all measurements. All incubations were at 30°C. Average results representative of three experiments are shown. Data are represented as mean ± SEM.](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_5257/pmc13015257/pmc13015257__gr6.jpg)