Topological analyses of the L-fucose-H+ symport protein, FucP, from Escherichia coli.
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.
Gunn
F J
FJ
Department of Biochemistry, University of Cambridge, UK.
Tate
C G
CG
Sansom
C E
CE
Henderson
P J
PJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005643:Fucose / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010405:Penicillinase / Q000235:genetics / Q000502:physiology; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D013329:Structure-Activity Relationship; D027981:Symporters; D013997:Time Factors
D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C088688:FucP protein, E coli; D011993:Recombinant Fusion Proteins; D027981:Symporters; D005643:Fucose; D010405:Penicillinase