Structure and Mechanism of the Lactose Permease of Escherichia coli

Membrane transport proteins that transduce free energy stored in electrochemical ion gradients into a concentration gradient are a major class of membrane proteins. We report the crystal structure at 3.5 angstroms of the Escherichia coli lactose permease, an intensively studied member of the major facilitator superfamily of transporters. The molecule is composed of N- and C-terminal domains, each with six transmembrane helices, symmetrically positioned within the permease. A large internal hydrophilic cavity open to the cytoplasmic side represents the inward-facing conformation of the transporter. The structure with a bound lactose homolog, β-D-galactopyranosyl-1-thio-β-D-galactopyranoside, reveals the sugar-binding site in the cavity, and residues that play major roles in substrate recognition and proton translocation are identified. We propose a possible mechanism for lactose/proton symport (co-transport) consistent with both the structure and a large body of experimental data.

[1]  S. Subramaniam,et al.  Structural Model for 12-Helix Transporters Belonging to the Major Facilitator Superfamily , 2003, Journal of bacteriology.

[2]  H. Kaback,et al.  A mutation in the lactose permease of Escherichia coli that decreases conformational flexibility and increases protein stability. , 2003, Biochemistry.

[3]  H. Kaback,et al.  Aromatic stacking in the sugar binding site of the lactose permease. , 2003, Biochemistry.

[4]  Lan Guan,et al.  An approach to membrane protein structure without crystals , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[5]  Satoshi Murakami,et al.  Crystal structure of bacterial multidrug efflux transporter AcrB , 2002, Nature.

[6]  H. Kaback,et al.  Changing the lactose permease of Escherichia coli into a galactose-specific symporter , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[7]  H. Kaback,et al.  Surface-exposed positions in the transmembrane helices of the lactose permease of Escherichia coli determined by intermolecular thiol cross-linking , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[8]  Manipulating conformational equilibria in the lactose permease of Escherichia coli. , 2002, Journal of molecular biology.

[9]  T. Nishio,et al.  The C-4 hydroxyl group of galactopyranosides is the major determinant for ligand recognition by the lactose permease of Escherichia coli. , 2001, Biochemistry.

[10]  H. Kaback,et al.  The kamikaze approach to membrane transport , 2001, Nature Reviews Molecular Cell Biology.

[11]  H. Kaback,et al.  Arg-302 facilitates deprotonation of Glu-325 in the transport mechanism of the lactose permease from Escherichia coli , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[12]  Kaback Hr,et al.  Functional estimation of loop-helix boundaries in the lactose permease of Escherichia coli by single amino acid deletion analysis. , 2001 .

[13]  Kaback Hr,et al.  Thiol cross-linking of transmembrane domains IV and V in the lactose permease of Escherichia coli. , 2000 .

[14]  J. Runner,et al.  Ligand recognition by the lactose permease of Escherichia coli: specificity and affinity are defined by distinct structural elements of galactopyranosides. , 2000, Biochemistry.

[15]  Christopher Miller,et al.  Ion channels: doing hard chemistry with hard ions. , 2000, Current opinion in chemical biology.

[16]  M. Saier.  Families of transmembrane sugar transport proteins , 2000, Molecular microbiology.

[17]  W. Hubbell,et al.  Proximity between Glu126 and Arg144 in the lactose permease of Escherichia coli. , 1999, Biochemistry.

[18]  J. Moeller,et al.  Fourier transform infrared analysis of purified lactose permease: a monodisperse lactose permease preparation is stably folded, alpha-helical, and highly accessible to deuterium exchange. , 1998, Biochemistry.

[19]  H. Kaback,et al.  Cys‐scanning mutagenesis: a novel approach to structure—function relationships in polytopic membrane proteins , 1998, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[20]  The substrate-binding site in the lactose permease of Escherichia coli. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[21]  H. Kaback,et al.  Fourier transform infrared spectroscopy reveals a rigid alpha-helical assembly for the tetrameric Streptomyces lividans K+ channel. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[22]  E A Merritt,et al.  Structural foundation for the design of receptor antagonists targeting Escherichia coli heat-labile enterotoxin. , 1997, Structure.

[23]  H. Kaback,et al.  The role of helix VIII in the lactose permease of Escherichia coli: II. Site‐directed sulfhydryl modification , 1997, Protein science : a publication of the Protein Society.

[24]  T. Tomizaki,et al.  The Whole Structure of the 13-Subunit Oxidized Cytochrome c Oxidase at 2.8 Å , 1996, Science.

[25]  B. Honig,et al.  Classical electrostatics in biology and chemistry. , 1995, Science.

[26]  K. Jung,et al.  Engineering a metal binding site within a polytopic membrane protein, the lactose permease of Escherichia coli. , 1995, Biochemistry.

[27]  R. Brooker,et al.  Functional roles of Glu-269 and Glu-325 within the lactose permease of Escherichia coli. , 1994, The Journal of biological chemistry.

[28]  M. L. Ujwal,et al.  Role of glutamate-269 in the lactose permease of Escherichia coli. , 1994, Molecular membrane biology.

[29]  H. Jung,et al.  Use of site-directed fluorescence labeling to study proximity relationships in the lactose permease of Escherichia coli. , 1993, Biochemistry.

[30]  H. Kaback,et al.  Functional interactions between putative intramembrane charged residues in the lactose permease of Escherichia coli. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[31]  J. Falke,et al.  Thermal motions of surface alpha-helices in the D-galactose chemosensory receptor. Detection by disulfide trapping. , 1992, Journal of molecular biology.

[32]  P. Henderson.  Proton-linked sugar transport systems in bacteria , 1990, Journal of bioenergetics and biomembranes.

[33]  C. Manoil,et al.  lac permease of Escherichia coli: topology and sequence elements promoting membrane insertion. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[34]  P. Roepe,et al.  Site-directed mutagenesis of tyrosine residues in the lac permease of Escherichia coli. , 1989, Biochemistry.

[35]  H. Kaback,et al.  Structure of the lac carrier protein of Escherichia coli. , 1983, The Journal of biological chemistry.

[36]  W. F. Widdas.  Inability of diffusion to account for placental glucose transfer in the sheep and consideration of the kinetics of a possible carrier transfer , 1952, The Journal of physiology.