Position 170 of Rabbit Na+/glucose cotransporter (rSGLT1) lies in the Na+ pathway; modulation of polarity/charge at this site regulates charge transfer and carrier turnover

Biophysical Journal
Steven A HuntleyMel Silverman

Abstract

Positions 163, 166, and 173, within the putative external loop joining transmembrane segments IV and V of rabbit Na(+)/glucose cotransporter, form part of its Na(+) interaction and voltage-sensing domain. Since a Q170C mutation within this region exhibits anomalous behavior, its function was further investigated. We used Xenopus oocytes coinjected with mouse T-antigen to enhance Q170C expression, and the two-microelectrode voltage-clamp technique. For Q170C, alpha-methyl D-glucopyranoside, phloridzin, and Na(+) affinity values are equivalent to those of wild-type; but turnover is reduced approximately 50%. Decreased [Na(+)] reduces Q170C, but not wild-type, charge transfer. Q170C presteady-state currents exhibit three time constants, tau, identical to wild-type. MTSES decreases maximal alpha-methyl D-glucopyranoside-induced currents by approximately 64% and Na(+) leak by approximately 55%; phloridzin and Na(+) affinity are unchanged. MTSES also reduces charge transfer (dithiothreitol-reversible) and Q170C turnover by approximately 60-70%. MTSEA and MTSET protect against MTSES, but neither affect Q170C function. MTSES has no obvious effect on the tau-values. Q170A behaves the same as Q170C. The mutation Q170E affects voltage sen...Continue Reading

References

Jan 1, 1992·The Journal of Membrane Biology·L ParentE M Wright
Jun 15, 1993·Proceedings of the National Academy of Sciences of the United States of America·D D LooE M Wright
Apr 26, 1996·The Journal of Biological Chemistry·M Panayotova-HeiermannE M Wright
Aug 15, 1997·The Journal of Biological Chemistry·M Panayotova-HeiermannE M Wright
May 29, 2003·Biophysical Journal·Daniel Krofchick, Mel Silverman

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Citations

Dec 14, 2011·American Journal of Physiology. Cell Physiology·Monica Sala-RabanalErnest M Wright
May 2, 2008·American Journal of Physiology. Cell Physiology·Tiemin LiuMel Silverman
Jun 24, 2006·Biochimica Et Biophysica Acta·Katsumi Nagata, Yoshio Hata
May 21, 2005·Biochimica Et Biophysica Acta·Dominique G GagnonJean-Yves Lapointe

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