Beta-galactoside Transport in E. Coli: A Functional Dissection of Lac Permease

Trends Biochem Sci. 1990 Aug;15(8):309-14. doi: 10.1016/0968-0004(90)90020-c.


The polytopic membrane protein lac permease harnesses energy from the electrochemical H+ gradient to transport beta-galactosidases against a concentration gradient. Although high-resolution structural information is still lacking, the permease is thought to possess 12 membrane-spanning alpha-helical segments. Various experimental strategies, including site-directed mutagenesis, have been employed to probe the function of this membrane protein at the molecular level.

Publication types

  • Review

MeSH terms

  • Amino Acid Sequence
  • Biological Transport
  • Escherichia coli / enzymology*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins*
  • Galactosides / metabolism*
  • Glycosides / metabolism*
  • Membrane Transport Proteins / physiology*
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins*
  • Symporters*


  • Escherichia coli Proteins
  • Galactosides
  • Glycosides
  • LacY protein, E coli
  • Membrane Transport Proteins
  • Monosaccharide Transport Proteins
  • Symporters
  • beta-galactoside
  • lactose permease