期刊
PLOS ONE
卷 6, 期 5, 页码 -出版社
PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0019677
关键词
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资金
- Agence Nationale de la Recherche [ANR-06-Blan-0420, ANR-PCV06-135269]
- CNRS
- Agence Nationale de la Recherche (ANR) [ANR-06-BLAN-0420] Funding Source: Agence Nationale de la Recherche (ANR)
Optimized protocols for achieving high-yield expression, purification and reconstitution of membrane proteins are required to study their structure and function. We previously reported high-level expression in Escherichia coli of active BmrC and BmrD proteins from Bacillus subtilis, previously named YheI and YheH. These proteins are half-transporters which belong to the ABC (ATP-Binding Cassette) superfamily and associate in vivo to form a functional transporter able to efflux drugs. In this report, high-yield purification and functional reconstitution were achieved for the heterodimer BmrC/BmrD. In contrast to other detergents more efficient for solubilizing the transporter, dodecyl-beta-D-maltoside (DDM) maintained it in a drug-sensitive and vanadate-sensitive ATPase-competent state after purification by affinity chromatography. High amounts of pure proteins were obtained which were shown either by analytical ultracentrifugation or gel filtration to form a monodisperse heterodimer in solution, which was notably stable for more than one month at 4 degrees C. Functional reconstitution using different lipid compositions induced an 8-fold increase of the ATPase activity (k(cat)similar to 5 s(-1)). We further validated that the quality of the purified BmrC/BmrD heterodimer is suitable for structural analyses, as its reconstitution at high protein densities led to the formation of 2-D crystals. Electron microscopy of negatively stained crystals allowed the calculation of a projection map at 20 angstrom resolution revealing that BmrC/BmrD might assemble into oligomers in a lipidic environment.
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