Document Detail


Differences in the substrate binding regions of renal organic anion transporters 1 (OAT1) and 3 (OAT3).
MedLine Citation:
PMID:  21543413     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
Bethzaida Astorga; Theresa M Wunz; Mark Morales; Stephen H Wright; Ryan M Pelis
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural     Date:  2011-05-04
Journal Detail:
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:
Created Date:  2011-08-05     Completed Date:  2011-10-03     Revised Date:  2013-06-30    
Medline Journal Info:
Nlm Unique ID:  100901990     Medline TA:  Am J Physiol Renal Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  F378-86     Citation Subset:  IM    
Affiliation:
Dept. of Pharmacology, College of Medicine, University of Arizona, Tucson, USA.
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MeSH Terms
Descriptor/Qualifier:
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:
1R01DK074022/DK/NIDDK NIH HHS; 5P30E006694//PHS HHS; 5T32HL07249/HL/NHLBI NIH HHS; DK752422/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
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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