Crystal structure of lactose permease in complex with an affinity inactivator yields unique insight into sugar recognition

Proc Natl Acad Sci U S A. 2011 Jun 7;108(23):9361-6. doi: 10.1073/pnas.1105687108. Epub 2011 May 18.

Abstract

Lactose permease of Escherichia coli (LacY) with a single-Cys residue in place of A122 (helix IV) transports galactopyranosides and is specifically inactivated by methanethiosulfonyl-galactopyranosides (MTS-gal), which behave as unique suicide substrates. In order to study the mechanism of inactivation more precisely, we solved the structure of single-Cys122 LacY in complex with covalently bound MTS-gal. This structure exhibits an inward-facing conformation similar to that observed previously with a slight narrowing of the cytoplasmic cavity. MTS-gal is bound covalently, forming a disulfide bond with C122 and positioned between R144 and W151. E269, a residue essential for binding, coordinates the C-4 hydroxyl of the galactopyranoside moiety. The location of the sugar is in accord with many biochemical studies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Substitution
  • Binding Sites / genetics
  • Biological Transport
  • Crystallization
  • Cysteine / chemistry
  • Cysteine / genetics
  • Cysteine / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Galactose / chemistry*
  • Galactose / metabolism
  • Lactose / chemistry
  • Lactose / metabolism
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Mesylates / chemistry
  • Mesylates / metabolism
  • Models, Molecular
  • Monosaccharide Transport Proteins / chemistry
  • Monosaccharide Transport Proteins / genetics
  • Monosaccharide Transport Proteins / metabolism
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary*
  • Substrate Specificity
  • Symporters / chemistry
  • Symporters / genetics
  • Symporters / metabolism
  • X-Ray Diffraction

Substances

  • Escherichia coli Proteins
  • Membrane Transport Proteins
  • Mesylates
  • Monosaccharide Transport Proteins
  • Symporters
  • methanethiosulfonate
  • lactose permease
  • Lactose
  • Cysteine
  • Galactose

Associated data

  • PDB/2Y5Y