| Differences in the substrate binding regions of renal organic anion transporters 1 (OAT1) and 3 (OAT3). | |
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MedLine Citation:
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PMID: 21543413 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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This study examined the selectivity of organic anion transporters OAT1 and OAT3 for structural congeners of the heavy metal chelator 2,3-dimercapto-1-propanesulfonic acid (DMPS). Thiol-reactive reagents were also used to test structural predictions based on a homology model of OAT1 structure. DMPS was near equipotent in its ability to inhibit OAT1 (IC(50) = 83 μM) and OAT3 (IC(50) = 40 μM) expressed in Chinese hamster ovary cells. However, removal of a thiol group (3-mercapto-1-propanesulfonic acid) resulted in a 2.5-fold increase in IC(50) toward OAT1 vs. a ∼55-fold increase in IC(50) toward OAT3. The data suggested that compound volume/size is important for binding to OAT1/OAT3. The sensitivity to HgCl(2) of OAT1 and OAT3 was also dramatically different, with IC(50) values of 104 and 659 μM, respectively. Consistent with cysteines of OAT1 being more accessible from the external medium than those of OAT3, thiol-reactive reagents reacted preferentially with OAT1 in cell surface biotinylation assays. OAT1 was less sensitive to HgCl(2) inhibition and less reactive toward membrane-impermeant thiol reactive reagents following mutation of cysteine 440 (C440) to an alanine. These data indicate that C440 in transmembrane helix 10 of OAT1 is accessible from the extracellular space. Indeed, C440 was exposed to the aqueous phase of the presumptive substrate translocation pathway in a homology model of OAT1 structure. The limited thiol reactivity in OAT3 suggests that the homologous cysteine residue (C428) is less accessible. Consistent with their homolog-specific selectivities, these data highlight structural differences in the substrate binding regions of OAT1 and OAT3. |
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Authors:
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Bethzaida Astorga; Theresa M Wunz; Mark Morales; Stephen H Wright; Ryan M Pelis |
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Publication Detail:
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Type: Comparative Study; Journal Article; Research Support, N.I.H., Extramural Date: 2011-05-04 |
Journal Detail:
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Title: American journal of physiology. Renal physiology Volume: 301 ISSN: 1522-1466 ISO Abbreviation: Am. J. Physiol. Renal Physiol. Publication Date: 2011 Aug |
Date Detail:
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Created Date: 2011-08-05 Completed Date: 2011-10-03 Revised Date: 2012-09-25 |
Medline Journal Info:
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Nlm Unique ID: 100901990 Medline TA: Am J Physiol Renal Physiol Country: United States |
Other Details:
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Languages: eng Pagination: F378-86 Citation Subset: IM |
Affiliation:
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Dept. of Pharmacology, College of Medicine, University of Arizona, Tucson, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Binding Sites CHO Cells Chelating Agents / pharmacokinetics* Cricetinae Cricetulus Humans Organic Anion Transport Protein 1 / metabolism* Organic Anion Transporters, Sodium-Independent / metabolism* Structural Homology, Protein Structure-Activity Relationship Unithiol / pharmacokinetics* |
| Grant Support | |
ID/Acronym/Agency:
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1R01DK074022/DK/NIDDK NIH HHS; 5P30E006694//PHS HHS; 5T32HL07249/HL/NHLBI NIH HHS; DK752422/DK/NIDDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Chelating Agents; 0/Organic Anion Transport Protein 1; 0/Organic Anion Transporters, Sodium-Independent; 0/organic anion transport protein 3; 4076-02-2/Unithiol |
| Comments/Corrections | |
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