Renal sodium-D-glucose cotransport system. Involvement of tyrosine residues in sodium-transporter interaction.
Using brush-border membrane vesicles isolated from calf kidney cortex the effect of tyrosine-reactive reagents on sodium-dependent D-glucose transport was investigated. Treatment of the membranes for 60 min with NBD-Cl (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole), N-acetylimidazole or tetranitromethane decreased D-glucose uptake 50, 70 and 40%, respectively. Tracer exchange experiments revealed that the inhibition of transport is due to a direct modification of the sodium-D-glucose cotransport system. The modification by NBD-Cl decreases the apparent Vmax of the transport system with respect to its interaction with sodium. In addition, the rate of inactivation of the transport system by NBD-Cl is reduced in the presence of high concentrations of sodium. The results indicate that tyrosine residues play an essential role in sodium-D-glucose cotransport and are probably involved in the binding and/or transport of sodium by the sodium-D-glucose cotransport system.
D000818:Animals; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D012964:Sodium / Q000378:metabolism; D014443:Tyrosine
D002352:Carrier Proteins; D009004:Monosaccharide Transport Proteins; D014443:Tyrosine; D012964:Sodium; D005947:Glucose