Structure of the Multidrug Resistance P-glycoprotein to 2.5 nm Resolution Determined by Electron Microscopy and Image Analysis

摘要: P-glycoprotein (P-gp) is a member of the ATP binding cassette superfamily active transporters and can confer multidrug resistance on cells tumors by pumping chemotherapeutic drugs from cytoplasm. P-gp was purified CHrB30 retained ability to bind substrates hydrolyze ATP. Labeling with lectin-gold particles suggested it monomeric. An initial structure determined 2.5 nm resolution electron microscopy single particle image analysis both detergent-solubilized lipid-reconstituted protein. The further refined three dimensional reconstructions images Fourier projection maps small two-dimensional crystalline arrays (unit cell parameters: a, 14.2 nm; b, 18.5 γ, 91.6°). When viewed above membrane plane protein toroidal, 6-fold symmetry diameter about 10 nm. There large central pore 5 in diameter, which closed at inner (cytoplasmic) face membrane, forming an aqueous chamber within membrane. opening this lipid phase present. perpendicular roughly rectangular maximum depth 8 two 3-nm lobes exposed cytoplasmic likely correspond nucleotide domains. This study provides first experimental insight into three-dimensional architecture any transporter.