Enzymes
| UniProtKB help_outline | 3 proteins |
Reaction participants Show >> << Hide
- Name help_outline nitrate Identifier CHEBI:17632 (Beilstein: 3587575; CAS: 14797-55-8) help_outline Charge -1 Formula NO3 InChIKeyhelp_outline NHNBFGGVMKEFGY-UHFFFAOYSA-N SMILEShelp_outline [O-][N+]([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 26 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline Na+ Identifier CHEBI:29101 (CAS: 17341-25-2) help_outline Charge 1 Formula Na InChIKeyhelp_outline FKNQFGJONOIPTF-UHFFFAOYSA-N SMILEShelp_outline [Na+] 2D coordinates Mol file for the small molecule Search links Involved in 259 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:71219 | RHEA:71220 | RHEA:71221 | RHEA:71222 | |
|---|---|---|---|---|
| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
| UniProtKB help_outline |
|
Publications
-
Thyroid Na+/I- symporter. Mechanism, stoichiometry, and specificity.
Eskandari S., Loo D.D., Dai G., Levy O., Wright E.M., Carrasco N.
The rat thyroid Na+/I-symporter (NIS) was expressed in Xenopus laevis oocytes and characterized using electrophysiological, tracer uptake, and electron microscopic methods. NIS activity was found to be electrogenic and Na+-dependent (Na+ >> Li+ >> H+). The apparent affinity constants for Na+ and I ... >> More
The rat thyroid Na+/I-symporter (NIS) was expressed in Xenopus laevis oocytes and characterized using electrophysiological, tracer uptake, and electron microscopic methods. NIS activity was found to be electrogenic and Na+-dependent (Na+ >> Li+ >> H+). The apparent affinity constants for Na+ and I- were 28 +/- 3 mM and 33 +/-9 microM, respectively. Stoichiometry of Na+/anion cotransport was 2:1. NIS was capable of transporting a wide variety of anions (I-, ClO3-, SCN-, SeCN-, NO3-, Br-, BF4-, IO4-, BrO3-, but perchlorate (ClO4-) was not transported. In the absence of anion substrate, NIS exhibited a Na+-dependent leak current (approximately 35% of maximum substrate-induced current) with an apparent Na+ affinity of 74 +/-14 mM and a Hill coefficient (n) of 1. In response to step voltage changes, NIS exhibited current transients that relaxed with a time constant of 8-14 ms. Presteady-state charge movements (integral of the current transients) versus voltage relations obey a Boltzmann relation. The voltage for half-maximal charge translocation (V0.5) was -15 +/-3 mV, and the apparent valence of the movable charge was 1. Total charge was insensitive to [Na+]o, but V0.5 shifted to more negative potentials as [Na+]o was reduced. NIS charge movements are attributed to the conformational changes of the empty transporter within the membrane electric field. The turnover rate of NIS was >/=22 s-1 in the Na+ uniport mode and >/=36 s-1 in the Na+/I-cotransport mode. Transporter density in the plasma membrane was determined using freeze-fracture electron microscopy. Expression of NIS in oocytes led to a approximately 2. 5-fold increase in the density of plasma membrane protoplasmic face intramembrane particles. On the basis of the kinetic results, we propose an ordered simultaneous transport mechanism in which the binding of Na+ to NIS occurs first. << Less
J. Biol. Chem. 272:27230-27238(1997) [PubMed] [EuropePMC]
This publication is cited by 4 other entries.