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The understanding of integral membrane protein (IMP) structure and function is hampered by the difficulty of handling these proteins. Aqueous solubilization, necessary for many types of biophysical analysis, generally requires a detergent to shield the large lipophilic surfaces of native IMPs. Many proteins remain difficult to study owing to a lack of(More)
An X-ray structure of the lactose permease of Escherichia coli (LacY) in an inward-facing conformation has been solved. LacY contains N- and C-terminal domains, each with six transmembrane helices, positioned pseudosymmetrically. Ligand is bound at the apex of a hydrophilic cavity in the approximate middle of the molecule. Residues involved in substrate(More)
Hexavalent chromium [Cr(VI)] has become a non-negligible pollutant in the world. Cr(VI) exposure leads to severe damage to the liver, but the mechanisms involved in Cr(VI)-mediated toxicity in the liver are unclear. The present study aimed to explore whether Cr(VI) induces energy metabolism disturbance and cell cycle arrest in human L-02 hepatocytes. We(More)
Here we describe an x-ray structure of wild-type lactose permease (LacY) from Escherichia coli determined by manipulating phospholipid content during crystallization. The structure exhibits the same global fold as the previous x-ray structures of a mutant that binds sugar but cannot catalyze translocation across the membrane. LacY is organized into two(More)
Helix V in LacY, which abuts and crosses helix I in the N-terminal helix bundle of LacY, contains Arg(144) and Trp(151), two residues that play direct roles in sugar recognition and binding, as well as Cys(154), which is important for conformational flexibility. In this study, paired Cys replacement mutants in helices V and I were strategically constructed(More)
Hexavalent chromium [Cr(VI)] and its compounds have extensive applications in many industries and are widely known to cause occupational diseases as well as carcinogenic effects in humans. Mitochondrial damage, which is important in Cr(VI)‑induced cytotoxicity, may be characterized by the opening status of the permeability transition pore, the maintenance(More)
Crystal structures of lactose permease from Escherichia coli (LacY) exhibit two six-helix bundles with 2-fold pseudosymmetry separated by a large hydrophilic cavity. The cavity is open only on the cytoplasmic side and contains the side chains important for both sugar and H(+) binding at the apex in the middle of the protein; the periplasmic side is tightly(More)
X-ray crystal structures of lactose permease (LacY) reveal pseudosymmetrically arranged N- and C-terminal six-transmembrane helix bundles surrounding a deep internal cavity open on the cytoplasmic side and completely closed on the periplasmic side. The residues essential for sugar recognition and H(+) translocation are located at the apex of the cavity and(More)
Cation-coupled active transport is an essential cellular process found ubiquitously in all living organisms. Here, we present two novel ligand-free X-ray structures of the lactose permease (LacY) of Escherichia coli determined at acidic and neutral pH, and propose a model for the mechanism of coupling between lactose and H+ translocation. No sugar-binding(More)
By using functional lactose permease devoid of native Cys residues with a discontinuity in the periplasmic loop between helices VII and VIII (N(7)/C(5) split permease), cross-linking between engineered paired Cys residues in helices VII and X was studied with the homobifunctional, thiol-specific cross-linkers 1,1-methanediyl bismethanethiosulfonate (3 A),(More)