Radiation-inactivation analysis of the oligomeric structure of the renal sodium/D-glucose symporter.
The radiation-inactivation size (RIS) of the rat renal brush-border membrane sodium/D-glucose cotransporter was estimated from the loss of transport activity in irradiated membrane vesicles. The RIS depended on the electrochemical conditions present when measuring transport activity. A RIS of 294 +/- 40 kDa was obtained when transport was measured in the presence of a sodium electrochemical gradient. Under sodium equilibrium conditions, the RIS was 84 +/- 25 kDa in the presence of a glucose gradient, and 92 +/- 20 kDa in its absence. In the absence of a sodium gradient, but in the presence of an electrical potential gradient, the RIS increased to 225 +/- 49 kDa. The 294 kDa result supports earlier suggestions that the Na+ gradient-dependent glucose transport activity is mediated by a tetramer. Individual monomers appear, however, to carry out glucose transport under equilibrium exchange conditions or when a glucose gradient serves as the only driving force. The electrical potential gradient-driven glucose transport RIS appears to involve three functional subunits.
Jetté
M
M
Laboratoire d'oncologie moléculaire, Université du Québec à Montréal, Canada.
Vachon
V
V
Potier
M
M
Béliveau
R
R
D000818:Animals; D004563:Electrochemistry; D007668:Kidney / Q000737:chemistry* / Q000528:radiation effects; D008297:Male; D008871:Microvilli / Q000737:chemistry / Q000528:radiation effects; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D009004:Monosaccharide Transport Proteins