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Title
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Glucose transport in the extremely thermoacidophilic Sulfolobus solfataricus involves a high-affinity membrane-integrated binding protein.
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Authors
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S.V.Albers,
M.G.Elferink,
R.L.Charlebois,
C.W.Sensen,
A.J.Driessen,
W.N.Konings.
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Ref.
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J Bacteriol, 1999,
181,
4285-4291.
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PubMed id
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Abstract
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The archaeon Sulfolobus solfataricus grows optimally at 80 degrees C and pH 2.5
to 3.5 on carbon sources such as yeast extracts, tryptone, and various sugars.
Cells rapidly accumulate glucose. This transport activity involves a
membrane-bound glucose-binding protein that interacts with its substrate with
very high affinity (Kd of 0. 43 microM) and retains high glucose affinity at
very low pH values (as low as pH 0.6). The binding protein was extracted with
detergent and purified to homogeneity as a 65-kDa glycoprotein. The gene coding
for the binding protein was identified in the S. solfataricus P2 genome by means
of the amino-terminal amino acid sequence of the purified protein. Sequence
analysis suggests that the protein is anchored to the membrane via an
amino-terminal transmembrane segment. Neighboring genes encode two membrane
proteins and an ATP-binding subunit that are transcribed in the reverse
direction, whereas a homologous gene cluster in Pyrococcus horikoshii OT3 was
found to be organized in an operon. These data indicate that S. solfataricus
utilizes a binding-protein-dependent ATP-binding cassette transporter for the
uptake of glucose.
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