Merck
  • Home
  • Search Results
  • Importance of cysteine residues in the thyroid hormone transporter MCT8.

Importance of cysteine residues in the thyroid hormone transporter MCT8.

Endocrinology (2013-04-03)
Elaine C Lima de Souza, Stefan Groeneweg, W Edward Visser, Robin P Peeters, Theo J Visser
ABSTRACT

The thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) is crucial for brain development as demonstrated by the severe psychomotor retardation in patients with MCT8 mutations. MCT8 contains 10 residues of the reactive amino acid cysteine (Cys) whose functional roles were studied using the Cys-specific reagent p-chloromercurybenzenesulfonate (pCMBS) and by site-directed mutagenesis. Pretreatment of JEG3 cells with pCMBS resulted in a dose- and time-dependent decrease of subsequent T3 uptake. Pretreatment with dithiothreitol did not affect TH transport or its inhibition by pCMBS. However, pCMBS inhibition of MCT8 was reversed by dithiothreitol. Inhibition of MCT8 by pCMBS was prevented in the presence of T3. The single and double mutation of C481A and C497A did not affect T3 transport, but the single mutants were less sensitive and the double mutant was completely insensitive to pCMBS. Similar effects on MCT8 were obtained using HgCl2 instead of pCMBS. In conclusion, we have identified Cys481 and Cys497 in MCT8 as the residues modified by pCMBS or HgCl2. These residues are probably located at or near the substrate-recognition site in MCT8. It remains to be investigated whether MCT8 function is regulated by modification of these Cys residues under pathophysiological conditions.

MATERIALS
Product Number
Brand
Product Description

Supelco
L-Alanine, certified reference material, TraceCERT®
Supelco
DL-Dithiothreitol solution, 1 M in H2O
Alanine, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
L-Alanine, ≥98% (TLC)
Sigma-Aldrich
L-Alanine, from non-animal source, meets EP, USP testing specifications, suitable for cell culture, 98.5-101.0%
Sigma-Aldrich
DL-Dithiothreitol, ≥99.0% (RT)
Supelco
L-Alanine, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
L-Alanine, ≥99%
Sigma-Aldrich
DL-Dithiothreitol solution, BioUltra, for molecular biology, ~1 M in H2O
Sigma-Aldrich
DL-Dithiothreitol, BioUltra, for molecular biology, ≥99.5% (RT)
Sigma-Aldrich
L-Alanine, ≥99.0% (NT)
Sigma-Aldrich
L-Alanine, BioUltra, ≥99.5% (NT)
Sigma-Aldrich
DL-Dithiothreitol, BioXtra, ≥99.0% (titration)
Sigma-Aldrich
DL-Dithiothreitol, ≥98% (HPLC), ≥99.0% (titration)
Sigma-Aldrich
DL-Dithiothreitol, for molecular biology, ≥98% (HPLC), ≥99% (titration)
Sigma-Aldrich
DL-Dithiothreitol, suitable for electrophoresis, ≥99%
Sigma-Aldrich
L-Alanine-12C3, 99.9 atom % 12C