The protocol for obtaining electrically sealed membrane vesicles from E. coli cells is presented. Proton pumps such as Complex I, quinol oxidase, and ATPase are active in the obtained vesicles. Quality of the preparation was tested by monitoring the electric potential generated by these pumps.
Studying of membrane enzymes often requires embedding them into the natural lipid environment. Inside-out, everted membrane vesicles allowed to explore effects of different substrates, inhibitors and other ligands on the operation of these enzymes. Functioning proton pumps, such as NADH: ubiquinone oxidoreductase Type 1 (Complex I), quinol oxidase, and ATPase also requires good electrical sealing of the vesicles. This protocol provides sufficient results in preparation of such vesicles for studying these enzymes (e.g., Euro et al., 2008; Belevich et al., 2011).
Materials and Reagents
Glass test tubes (approximately 10 x 90 mm)
E. coli MWC215 (SmR ndh::CmR) or GR70N (wild type or mutated) cells grown under aeration
Luria Broth or other medium suitable for aerobic growth of E. coli culture
Antibiotics, as required for particular E. coli strain
Lysozyme
Ethylenediaminetetraacetic acid (EDTA)
Magnesium sulfate (MgSO4)
Dithiothreitol (DTT)
Phenylmethylsulfonyl fluoride (PMSF)
Ethanol
Liquid N2
Electric potential-sensitive probe Oxonol VI (Sigma-Aldrich, catalog number: 75926 )