Electrogenic nature of rat sodium-dependent multivitamin transport.
We report on the electrogenic nature of the transport process mediated by the rat sodium-dependent multivitamin transporter. In Cos-7 cells, the relationship of Na(+) concentration versus biotin and pantothenate uptake rate was sigmoidal with a Na(+):substrate stoichiometry of 2:1. In Cos-7 cells expressing rat SMVT biotin transport was significantly higher when the membrane was hyperpolarized and considerably reduced when the membrane was depolarized. Similarly, biotin uptake in X. laevis oocytes expressing rat SMVT was inhibited with depolarized oocyte membrane by altering the K(+) permeability across the membrane. It is concluded that the transport of biotin and pantothenate mediated by rat SMVT is electrogenic with a Na(+):substrate coupling ratio of 2:1 and that the transport process is associated with the transfer of one net positive charge across the membrane per transport cycle.
Prasad
P D
PD
Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, Georgia 30912, USA. pprasad@mail.mcg.edu
Srinivas
S R
SR
Wang
H
H
Leibach
F H
FH
Devoe
L D
LD
Ganapathy
V
V
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D001710:Biotin / Q000378:metabolism; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D005260:Female; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials; D009865:Oocytes / Q000502:physiology; D010205:Pantothenic Acid / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D027981:Symporters; D014162:Transfection; D014982:Xenopus laevis
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D027981:Symporters; C119981:biotin transporter; D010205:Pantothenic Acid; D001464:Barium; D001710:Biotin; D012964:Sodium; D011188:Potassium