Publication Abstract from PubMed
The structure of the N-terminal transmembrane domain (residues 1-34) of subunit b of the Escherichia coli F0F1-ATP synthase has been solved by two-dimensional 1H NMR in a membrane mimetic solvent mixture of chloroform/methanol/H2O (4:4:1). Residues 4-22 form an alpha-helix, which is likely to span the hydrophobic domain of the lipid bilayer to anchor the largely hydrophilic subunit b in the membrane. The helical structure is interrupted by a rigid bend in the region of residues 23-26 with alpha-helical structure resuming at Pro-27 at an angle offset by 20 degrees from the transmembrane helix. In native subunit b, the hinge region and C-terminal alpha-helical segment would connect the transmembrane helix to the cytoplasmic domain. The transmembrane domains of the two subunit b in F0 were shown to be close to each other by cross-linking experiments in which single Cys were substituted for residues 2-21 of the native subunit and b-b dimer formation tested after oxidation with Cu(II)(phenanthroline)2. Cys residues that formed disulfide cross-links were found with a periodicity indicative of one face of an alpha-helix, over the span of residues 2-18, where Cys at positions 2, 6, and 10 formed dimers in highest yield. A model for the dimer is presented based upon the NMR structure and distance constraints from the cross-linking data. The transmembrane alpha-helices are positioned at a 23 degrees angle to each other with the side chains of Thr-6, Gln-10, Phe-14, and Phe-17 at the interface between subunits. The change in direction of helical packing at the hinge region may be important in the functional interaction of the cytoplasmic domains.
Structure of the membrane domain of subunit b of the Escherichia coli F0F1 ATP synthase.,Dmitriev O, Jones PC, Jiang W, Fillingame RH J Biol Chem. 1999 May 28;274(22):15598-604. PMID:10336456[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
