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Gene Review

lacY  -  galactoside permease

Escherichia coli UTI89

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Disease relevance of lacY


High impact information on lacY


Chemical compound and disease context of lacY


Biological context of lacY


Anatomical context of lacY

  • Because of the extensive aggregation of lactose permease synthesized in the absence of membranes, only low amounts originating from the soluble enzyme pool integrated posttranslationally into the membrane vesicles [16].
  • The lactose permease of Escherichia coli catalyzes coupled translocation of galactosides and H(+) across the cell membrane [17].
  • Epitope 4B1 is readily detectable in spheroplasts and right-side-out membrane vesicles from PE-containing but not from PE-deficient cells expressing lactose permease [18].
  • This is interpreted as evidence for two different conformations of lactose permease, one with the binding site open to the cytoplasm and closed to the periplasm and vice versa for the other state [19].
  • From similar experiments with N-terminal segments of lactose permease, we estimate that at most a polypeptide of 120 amino acid residues emerging from the ribosome is needed to target the nascent chain to the lipid bilayer and to mediate attachment of the ribosome to the membrane during elongation [20].

Associations of lacY with chemical compounds

  • Moreover, membrane vesicles when present cotranslationally during synthesis of lactose permease, acquired the capability to accumulate lactose, strongly suggesting a correct in vitro assembly of the enzyme [16].
  • Site-directed N-ethylmaleimide labeling was studied with Glu-126 and/or Arg-144 mutants in lactose permease containing a single, native Cys residue at position 148 in the substrate-binding site [21].
  • Thus, three individual cysteine residues were introduced into putative helix IV of a lactose permease mutant devoid of native cysteine residues containing a high-affinity divalent metal ion binding site in the form of six contiguous histidine residues in the periplasmic loop between helices III and IV [22].
  • Regulation of lactose permease activity by the phosphoenolpyruvate:sugar phosphotransferase system: evidence for direct binding of the glucose-specific enzyme III to the lactose permease [23].
  • Treatment of lactose permease with N-ethylmaleimide, which blocks ligand binding and transport by alkylating Cys-148, also blocks enzyme IIAglc binding [15].

Regulatory relationships of lacY


Analytical, diagnostic and therapeutic context of lacY


  1. In vitro and in vivo products of E. coli lactose permease gene are identical. Ehring, R., Beyreuther, K., Wright, J.K., Overath, P. Nature (1980) [Pubmed]
  2. Structure and function of facilitative sugar transporters. Barrett, M.P., Walmsley, A.R., Gould, G.W. Curr. Opin. Cell Biol. (1999) [Pubmed]
  3. Effects of the putative neutrophil-generated toxin, hypochlorous acid, on membrane permeability and transport systems of Escherichia coli. Albrich, J.M., Gilbaugh, J.H., Callahan, K.B., Hurst, J.K. J. Clin. Invest. (1986) [Pubmed]
  4. Structural evidence for induced fit and a mechanism for sugar/H+ symport in LacY. Mirza, O., Guan, L., Verner, G., Iwata, S., Kaback, H.R. EMBO J. (2006) [Pubmed]
  5. Elucidation of substrate binding interactions in a membrane transport protein by mass spectrometry. Weinglass, A.B., Whitelegge, J.P., Hu, Y., Verner, G.E., Faull, K.F., Kaback, H.R. EMBO J. (2003) [Pubmed]
  6. A polytopic membrane protein displays a reversible topology dependent on membrane lipid composition. Bogdanov, M., Heacock, P.N., Dowhan, W. EMBO J. (2002) [Pubmed]
  7. Phospholipid-assisted protein folding: phosphatidylethanolamine is required at a late step of the conformational maturation of the polytopic membrane protein lactose permease. Bogdanov, M., Dowhan, W. EMBO J. (1998) [Pubmed]
  8. The size of the lactose permease derived from rotational diffusion measurements. Dornmair, K., Corin, A.F., Wright, J.K., Jähnig, F. EMBO J. (1985) [Pubmed]
  9. Site-directed alkylation and the alternating access model for LacY. Kaback, H.R., Dunten, R., Frillingos, S., Venkatesan, P., Kwaw, I., Zhang, W., Ermolova, N. Proc. Natl. Acad. Sci. U.S.A. (2007) [Pubmed]
  10. Deduction of consensus binding sequences on proteins that bind IIAGlc of the phosphoenolpyruvate:sugar phosphotransferase system by cysteine scanning mutagenesis of Escherichia coli lactose permease. Sondej, M., Sun, J., Seok, Y.J., Kaback, H.R., Peterkofsky, A. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  11. Changing the lactose permease of Escherichia coli into a galactose-specific symporter. Guan, L., Sahin-Toth, M., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (2002) [Pubmed]
  12. Variable coordination of cotranscribed genes in Escherichia coli following antisense repression. Dryselius, R., Nikravesh, A., Kulyt??, A., Goh, S., Good, L. BMC Microbiol. (2006) [Pubmed]
  13. Conformational flexibility at the substrate binding site in the lactose permease of Escherichia coli. Weinglass, A.B., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  14. Arg-302 facilitates deprotonation of Glu-325 in the transport mechanism of the lactose permease from Escherichiacoli. Sahin-Toth, M., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  15. Topology of allosteric regulation of lactose permease. Seok, Y.J., Sun, J., Kaback, H.R., Peterkofsky, A. Proc. Natl. Acad. Sci. U.S.A. (1997) [Pubmed]
  16. In vitro membrane assembly of a polytopic, transmembrane protein results in an enzymatically active conformation. Ahrem, B., Hoffschulte, H.K., Müller, M. J. Cell Biol. (1989) [Pubmed]
  17. An approach to membrane protein structure without crystals. Sorgen, P.L., Hu, Y., Guan, L., Kaback, H.R., Girvin, M.E. Proc. Natl. Acad. Sci. U.S.A. (2002) [Pubmed]
  18. A phospholipid acts as a chaperone in assembly of a membrane transport protein. Bogdanov, M., Sun, J., Kaback, H.R., Dowhan, W. J. Biol. Chem. (1996) [Pubmed]
  19. Orientation of substrate and two conformations of lactose permease. Dornmair, K., Jähnig, F. Biochemistry (1988) [Pubmed]
  20. The N-terminal region of Escherichia coli lactose permease mediates membrane contact of the nascent polypeptide chain. Stochaj, U., Ehring, R. Eur. J. Biochem. (1987) [Pubmed]
  21. The substrate-binding site in the lactose permease of Escherichia coli. Venkatesan, P., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  22. Distance determination in proteins using designed metal ion binding sites and site-directed spin labeling: application to the lactose permease of Escherichia coli. Voss, J., Hubbell, W.L., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  23. Regulation of lactose permease activity by the phosphoenolpyruvate:sugar phosphotransferase system: evidence for direct binding of the glucose-specific enzyme III to the lactose permease. Osumi, T., Saier, M.H. Proc. Natl. Acad. Sci. U.S.A. (1982) [Pubmed]
  24. Sugar transport by the bacterial phosphotransferase system. In vivo regulation of lactose transport in Escherichia coli by IIIGlc, a protein of the phosphoenolpyruvate:glycose phosphotransferase system. Mitchell, W.J., Saffen, D.W., Roseman, S. J. Biol. Chem. (1987) [Pubmed]
  25. The structure of the lactose permease derived from Raman spectroscopy and prediction methods. Vogel, H., Wright, J.K., Jähnig, F. EMBO J. (1985) [Pubmed]
  26. Manipulating phospholipids for crystallization of a membrane transport protein. Guan, L., Smirnova, I.N., Verner, G., Nagamori, S., Kaback, H.R. Proc. Natl. Acad. Sci. U.S.A. (2006) [Pubmed]
  27. Energetics of Ligand-induced Conformational Flexibility in the Lactose Permease of Escherichia coli. Nie, Y., Smirnova, I., Kasho, V., Kaback, H.R. J. Biol. Chem. (2006) [Pubmed]
  28. Sequence alignment and homology threading reveals prokaryotic and eukaryotic proteins similar to lactose permease. Kasho, V.N., Smirnova, I.N., Kaback, H.R. J. Mol. Biol. (2006) [Pubmed]
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