Additive and independent responses in a single receptor: aspartate and maltose stimuli on the tar protein

Cell. 1987 Jul 17;50(2):171-80. doi: 10.1016/0092-8674(87)90213-3.


The aspartate and maltose responses of E. coli are mediated through a single membrane receptor, yet the responses are independent and additive. Both stimuli cause methylation of the same 4 glutamic acid residues. More extensive methylation occurs when a cell that has adapted to one stimulus is exposed to the second, or when both stimuli are added simultaneously. The degree of methylation, as well as receptor migration on two-dimensional gels, demonstrates that only one type of protein is involved, rather than two different receptors arising from differential processing of a single gene. A conformational "push-pull" mechanism in which binding of stimulus and covalent modification, producing opposing stresses, can explain these diverse results.

Publication types

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

MeSH terms

  • ATP-Binding Cassette Transporters*
  • Aspartic Acid / pharmacology*
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Escherichia coli / drug effects
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Genes
  • Genes, Bacterial
  • Maltose / metabolism
  • Maltose / pharmacology*
  • Maltose-Binding Proteins
  • Methylation
  • Models, Biological
  • Monosaccharide Transport Proteins*
  • Mutation
  • Plasmids


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • Maltose-Binding Proteins
  • Monosaccharide Transport Proteins
  • maltose transport system, E coli
  • Aspartic Acid
  • Maltose