Na+-to-sugar stoichiometry of SGLT3

Am J Physiol Renal Physiol. 2001 Feb;280(2):F278-82. doi: 10.1152/ajprenal.2001.280.2.F278.

Abstract

Sodium-glucose cotransporters (SGLTs) mediate active transport of sugar across cell membranes coupled to Na+, by using the electrochemical gradient as a driving force. In the kidney, there is evidence for two kinds of cotransporters, a high-affinity, low-capacity system, and a low-affinity, high-capacity system, with differences in substrate specificity and kinetics. Three renal SGLT clones have been identified: SGLT1 corresponding to the high-affinity system, and SGLT2 and SGLT3 with properties reminiscent of the low-affinity system. We have determined the stoichiometry of pig SGLT3 (pSGLT3) by using a direct method, comparing the substrate-induced inward charge to 22Na or [14C]alpha-methyl-D-glucopyranoside uptake in the same oocyte. pSGLT3 stoichiometry is 2 Na+:1 sugar, the same as that for SGLT1, but different from SGLT2 (1:1). The Na+ Hill coefficient for SGLT3 is approximately 1.5, suggesting low cooperativity between Na+ binding sites. Thus SGLT3 has functional characteristics intermediate between SGLT1 and SGLT2, so, whereas SGLT3 stoichiometry is the same as that for SGLT1 (2:1), sugar affinity and specificity are similar to SGLT2.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Transport System X-AG*
  • Animals
  • Carbohydrates / pharmacokinetics*
  • Carrier Proteins / metabolism*
  • Glutamate Plasma Membrane Transport Proteins
  • Humans
  • Intestinal Mucosa / metabolism
  • Kidney / metabolism*
  • Membrane Glycoproteins / metabolism
  • Monosaccharide Transport Proteins / chemistry
  • Monosaccharide Transport Proteins / metabolism*
  • Rabbits
  • Rats
  • Sodium Chloride / pharmacokinetics*
  • Sodium-Glucose Transport Proteins
  • Sodium-Glucose Transporter 1
  • Sodium-Glucose Transporter 2
  • Swine
  • Symporters*
  • Xenopus laevis

Substances

  • Amino Acid Transport System X-AG
  • Carbohydrates
  • Carrier Proteins
  • Glutamate Plasma Membrane Transport Proteins
  • Membrane Glycoproteins
  • Monosaccharide Transport Proteins
  • SLC5A1 protein, human
  • SLC5A2 protein, human
  • SLC5A4 protein, human
  • Slc5a1 protein, rat
  • Slc5a2 protein, rat
  • Sodium-Glucose Transport Proteins
  • Sodium-Glucose Transporter 1
  • Sodium-Glucose Transporter 2
  • Symporters
  • Sodium Chloride