Merck
  • Home
  • Search Results
  • Structural variation governs substrate specificity for organic anion transporter (OAT) homologs. Potential remote sensing by OAT family members.

Structural variation governs substrate specificity for organic anion transporter (OAT) homologs. Potential remote sensing by OAT family members.

The Journal of biological chemistry (2007-06-08)
Gregory Kaler, David M Truong, Akash Khandelwal, Megha Nagle, Satish A Eraly, Peter W Swaan, Sanjay K Nigam
ABSTRACT

Organic anion transporters (OATs, SLC22) interact with a remarkably diverse array of endogenous and exogenous organic anions. However, little is known about the structural features that determine their substrate selectivity. We examined the substrate binding preferences and transport function of olfactory organic anion transporter, Oat6, in comparison with the more broadly expressed transporter, Oat1 (first identified as NKT). In analyzing interactions of both transporters with over 40 structurally diverse organic anions, we find a correlation between organic anion potency (pKi) and hydrophobicity (logP) suggesting a hydrophobicity-driven association with transporter-binding sites, which appears particularly prominent for Oat6. On the other hand, organic anion binding selectivity between Oat6 and Oat1 is influenced by the anion mass and net charge. Smaller mono-anions manifest greater potency for Oat6 and di-anions for Oat1. Comparative molecular field analysis confirms these mechanistic insights and provides a model for predicting new OAT substrates. By comparative molecular field analysis, both hydrophobic and charged interactions contribute to Oat1 binding, although it is predominantly the former that contributes to Oat6 binding. Together, the data suggest that, although the three-dimensional structures of these two transporters may be very similar, the binding pockets exhibit crucial differences. Furthermore, for six radiolabeled substrates, we assessed transport efficacy (Vmax) for Oat6 and Oat1. Binding potency and transport efficacy had little correlation, suggesting that different molecular interactions are involved in substrate binding to the transporter and translocation across the membrane. Substrate specificity for a particular transporter may enable design of drugs for targeting to specific tissues (e.g. olfactory mucosa). We also discuss how these data suggest a possible mechanism for remote sensing between OATs in different tissue compartments (e.g. kidney, olfactory mucosa) via organic anions.

MATERIALS
Product Number
Brand
Product Description

Supelco
Ochratoxin A, from Aspergillus ochraceus, reference material
Supelco
Salicylic acid, certified reference material, TraceCERT®
Sigma-Aldrich
Penicillin G sodium salt, ~1650 U/mg
Sigma-Aldrich
Ochratoxin A, from Petromyces albertensis, ≥98% (HPLC)
Sigma-Aldrich
Penicillin G sodium salt, powder, BioReagent, suitable for cell culture
Supelco
Ibuprofen
Sigma-Aldrich
Prostaglandin E2, γ-irradiated, powder, BioXtra, suitable for cell culture
Sigma-Aldrich
p-Aminohippuric acid, ≥99%
Sigma-Aldrich
Acetylsalicylic acid, ≥99.0%
Sigma-Aldrich
Prostaglandin E2, synthetic, powder, BioReagent, suitable for cell culture
Sigma-Aldrich
3-Hydroxybutyric acid, 95%
Sigma-Aldrich
Salicylic acid, suitable for plant cell culture
Sigma-Aldrich
Salicylic acid, BioXtra, ≥99.0%
Sigma-Aldrich
Ibuprofen, meets USP testing specifications
Sigma-Aldrich
Ibuprofen, ≥98% (GC)
Sigma-Aldrich
Salicylic acid, meets analytical specification of Ph. Eur., BP, USP, 99.5-100.5% (calc. to the dried substance)
Sigma-Aldrich
Hexanoic acid, purum, ≥98.0% (GC)
Supelco
Hexanoic acid, analytical standard
Sigma-Aldrich
Hippuric acid, 98%
Sigma-Aldrich
Salicylic acid, ≥99%, FG
Sigma-Aldrich
Glutaric acid, 99%
Sigma-Aldrich
Salicylic acid, ACS reagent, ≥99.0%
Sigma-Aldrich
Acetylsalicylic acid, analytical standard
Sigma-Aldrich
Prostaglandin E2, ≥93% (HPLC), synthetic
Sigma-Aldrich
Salicylic acid, puriss. p.a., ≥99.0% (T)
Sigma-Aldrich
N-Acetyl-L-aspartic acid, ≥99.0% (T)
Sigma-Aldrich
(S)-(+)-2-Methylbutyric acid, 98%
Supelco
Mettler-Toledo Calibration substance ME 18555, Benzoic acid, analytical standard, for the calibration of the thermosystem 900, traceable to primary standards (LGC)
Sigma-Aldrich
Salicylic acid, ReagentPlus®, ≥99%
Sigma-Aldrich
(S)-(+)-2-Hydroxy-3-methylbutyric acid, 99%, optical purity ee: 99% (GLC)