Mutational analysis of histidine residues in human organic anion transporter 4 (hOAT4)

Fanfan Zhou, Zui Pan, Jianjie Ma, Guofeng You

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15 Scopus citations


Human organic anion transporter 4 (hOAT4) belongs to a family of organic anion transporters which play critical roles in the body disposition of clinically important drugs, including anti-HIV therapeutics, antitumour drugs, antibiotics, anti-hypertensives and anti-inflammatories. hOAT4-mediated transport of the organic anion oestrone sulphate in COS-7 cells was inhibited by the histidine-modifying reagent DEPC (diethyl pyrocarbonate). Therefore the role of histidine residues in the function of hOAT4 was examined by site-directed mutagenesis. All five histidine residues of hOAT4 were converted into alanine, singly or in combination. Single replacement of His-47, or simultaneous replacement of His-47/52/83 or His-47/52/83/305/469 (H-less) led to a 50-80% decrease in transport activity. The decreased transport activity of these mutants was correlated with a decreased amount of cell-surface expression, although the total cell expression of these mutants was similar to that of wild-type hOAT4. These results suggest that mutation at positions 47, 47/52/83 and 47/52/83/305/469 impaired membrane expression rather than function. We also showed that, although most of the histidine mutants of hOAT4 were sensitive to inhibition by DEPC, H469A (His-469 → Ala) was completely insensitive to inhibition by this reagent. Therefore modification of His-469 is responsible for the inhibition of hOAT4 by DEPC.

Original languageEnglish (US)
Pages (from-to)87-92
Number of pages6
JournalBiochemical Journal
Issue number1
StatePublished - Nov 15 2004

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


  • COS-7 cell
  • Diethyl pyrocarbonate (DEPC)
  • Histidine
  • Human organic anion transporter 4 (hOAT4)
  • Mutagenesis
  • Oestrone sulphate


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