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Molecular basis for the differential sensitivity of OCT2 and OAT1 toward Hg 2+
Author(s) -
Astorga Bethzaida Olivia,
Pelis Ryan M,
Wunz Theresa M,
Perry Jennifer A,
Pritchard John R.,
Wright Stephen H
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a908
Subject(s) - chemistry , organic anion transporter 1 , chinese hamster ovary cell , cysteine , epithelial polarity , biochemistry , multidrug resistance associated protein 2 , kidney , cotransporter , binding site , transporter , receptor , membrane , biology , enzyme , endocrinology , atp binding cassette transporter , organic chemistry , gene , sodium
Organic anion (OAT) and cation (OCT) transporters in the SLC22A family are located on the basolateral membrane of renal proximal tubule cells and mediate the uptake and subsequent secretion of potentially toxic organic electrolytes. We hypothesized that inorganic mercury, which is highly toxic to renal tubules, would interact with cysteines in OAT1 and OCT2 and reduce their transport activities. HgCl 2 did inhibit the transport activity of both human OAT1 and OCT2 stably expressed in Chinese hamster ovary cells, but interestingly, hOCT2 was more sensitive to HgCl 2 than hOAT1 (IC50: 4 ± 0.5 μM vs. 35 ± 12.0 μM). Examination of 3D homology models of hOAT1 and hOCT2 structure indicated marked differences in the relative location of cysteine residues, with cysteines in OCT2 more proximal to the proposed site of substrate‐protein interaction. A thiol‐reactive biotinylation reagent reacted much more efficiently with OCT2 than with OAT1, and OCT2 was less sensitive to HgCl 2 after removing four cysteines in the proposed binding region. OAT1’s reduced sensitivity to mercury may be explained by differences in the relative position of cysteines within the structures of OAT1 and OCT2. (supported by DK58251)