Functionality of a membrane protein in bicelles

Bicelles are bilayered discoidal lipid-detergent assemblies which are useful as model membranes. To date, there has been no direct demonstration of functional viability for an integral membrane protein reconstituted into bicelles, In this contribution, the catalytic activity of diacylglycerol kinase (DAGK) was measured following reconstitution into several different bicelle systems and compared to activities measured in traditional mixed micelles and vesicles, For the most optimal bicelle systems tested, DAGK activities approached those observed in mixed micelles or vesicles, For some other bicellar mixtures tested, activities were much lower, with steady-state kinetic data indicating reduced V-max rather than perturbations in substrate K-m, Catalytically, DAGK showed a strong preference for bicelles containing 3-(cholamidopropyl)dimethylammonio-2-hydroxy-1-propanesulfonate (CHAPSO) as the detergent component relative to short-chained phosphatidylcholine, DAGK also exhibited a preference for dimyristoylphosphatidylcholine or dipalmitoylphosphatidylcholine bicelles relative to those of dilauroylphosphatidylcholine. (C) 2000 Academic Press.