Water transport through the sodium-glucose cotransporter SGLT1
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
10th European Biophysics Congress
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
The intestine reabsorbs about nine liters of water daily.
A primary role in that water uptake has been ascribed to
secondary active transporters that are thought to couple
water transport to sodium transport along its concentration
gradient. In contrast, homology structure-based molecular
dynamics simulations suggest passive water movement
through the most prominent member of the water transporting
carrier family, the sodium-glucose cotransporter
SGLT1. However, their calculated turnover numbers are
three to four orders of magnitude higher than those determined
experimentally. To clarify the water transporting
mechanism of SGLT1, we used a previously established
assay for determining the single molecule water permeability,
pf , for transporters in epithelial cell monolayers.
That is, we measured the dilution of an aqueous dye in
the immediate vicinity of the monolayer and determined
the abundance of the EGFP-tagged SGLT1 transporter
in the apical and basolateral membranes by fluorescence
correlation spectroscopy. The pf value compares well to
that reported for aquaporins. It indicates the presence of
a passive water channel and is thus not compatible with
secondary active water transport. We obtained independent
proof by reconstituting the purified SGLT1 into lipid vesicles.
Forschungs-