Topological analyses of the L-fucose-H+ symport protein, FucP, from Escherichia coli

Mol Microbiol. 1995 Feb;15(4):771-83. doi: 10.1111/j.1365-2958.1995.tb02384.x.


The transport of L-fucose into Escherichia coli is mediated by the L-fucose-H+ symport protein (FucP). The fucP gene has been sequenced and encodes a hydrophobic protein that contains 438 amino acid residues, with a predicted M(r) of 47,773. The hydropathic profile of FucP indicates 10 to 12 hydrophobic regions that could span the membrane as alpha-helices. A 12-helix model with the N- and C-termini located in the cytoplasm was derived from the hydropathic profile and from application of the 'positive inside' rule. This model was tested using beta-lactamase fusion technology. Analyses of 62 different FucP-beta-lactamase fusions suggested that the FucP protein crosses the cytoplasmic membrane of E. coli 12 times, with the N- and C-termini in the cytoplasm. From measurements of [14C]-L-fucose uptake, it was deduced that the last putative transmembrane region must be complete for transport activity to be retained and that the four C-terminal residues were unnecessary for transport activity. Fourier transform analyses show that all the predicted helices contain a periodicity that enables hydrophobic/hydrophilic faces to be identified; these were particularly evident in putative helices 1, 3, 4, 5, 6, 10 and 11.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Western
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Fucose / metabolism*
  • Models, Biological
  • Molecular Sequence Data
  • Penicillinase / genetics
  • Penicillinase / physiology
  • Protein Structure, Secondary
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / physiology
  • Structure-Activity Relationship
  • Symporters*
  • Time Factors


  • Carrier Proteins
  • Escherichia coli Proteins
  • FucP protein, E coli
  • Recombinant Fusion Proteins
  • Symporters
  • Fucose
  • Penicillinase