In mammalian cells the uptake of glucose is mediated by a family of closely
related transport proteins which are called the glucose transporters [1,2,3].
At least seven of these transporters are currently known to exist (in Human
they are encoded by the GLUT1 to GLUT7 genes).
These integral membrane proteins are predicted to comprise twelve membrane
spanning domains. The glucose transporters show sequence similarities [4,5]
with a number of other sugar or metabolite transport proteins listed below
(references are only provided for recently determined sequences).
Escherichia coli arabinose-proton symport (araE).
Escherichia coli galactose-proton symport (galP).
Escherichia coli and Klebsiella pneumoniae citrate-proton symport (also
known as citrate utilization determinant) (gene cit).
Leishmania enriettii probable transport protein (LTP).
Yeast hypothetical proteins YBR241c, YCR98c and YFL040w.
Caenorhabditis elegans hypothetical protein ZK637.1.
Escherichia coli hypothetical proteins yabE, ydjE and yhjE.
Haemophilus influenzae hypothetical proteins HI0281 and HI0418.
Bacillus subtilis hypothetical proteins yxbC and yxdF.
It has been suggested  that these transport proteins have evolved from the
duplication of an ancestral protein with six transmembrane regions, this
hypothesis is based on the conservation of two G-R-[KR] motifs. The first one
is located between the second and third transmembrane domains and the second
one between transmembrane domains 8 and 9.
We have developed two patterns to detect this family of proteins. The first
pattern is based on the G-R-[KR] motif; but because this motif is too short to
be specific to this family of proteins, we have derived a pattern from a
larger region centered on the second copy of this motif. The second pattern
is based on a number of conserved residues which are located at the end of the
fourth transmembrane segment and in the short loop region between the fourth
and fifth segments.
April 2006 / Patterns revised.
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