Experimental tests of a homology model for OxlT, the oxalate transporter of Oxalobacter formigenes

Qiang Yang, Xicheng Wang, Liwen Ye, Mark Mentrikoski, Elham Mohammadi, Young Mog Kim, Peter C. Maloney

Research output: Contribution to journalArticle

Abstract

Using the x-ray structure of the glycerol 3-phosphate transporter (GlpT), we devised a model for the distantly related oxalate transporter, OxlT. The model accommodates all earlier biochemical information on OxlT, including the idea that Lys-355 lies on the permeation pathway, and predicts that Lys-355 and a second positive center, Arg-272, comprise the binding site for divalent oxalate. Study of R272K, R272A, and R272Q derivatives verifies that Arg-272 is essential, and comparisons with GlpT show that both anion transporters bind substrates within equivalent domains. In 22 single-cysteine variants in TM7 and TM8, topology as marked by accessibility to Oregon green maleimide is predicted by the model, with similar concordance for 52 positions probed earlier. The model also reconciles cross-linking of a cysteine pair placed near the periplasmic ends of TM2 and TM7, and retrospective study of TM2 and TM11 confirms that positions supporting disulfide trapping lie at a helical interface. Our work describes a pathway to the modeling of OxlT and other transporters in the major facilitator superfamily and outlines simple experimental tests to evaluate such proposals.

Original languageEnglish (US)
Pages (from-to)8513-8518
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number24
DOIs
StatePublished - Jun 14 2005

Keywords

  • Anion-binding
  • Disulfide trapping
  • Major facilitator superfamily
  • Membrane protein
  • Permeation pathway

ASJC Scopus subject areas

  • General

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