Structure-Function Analysis of the Bestrophin Family of Anion Channels

Takashi Tsunenari, Hui Sun, John Williams, Hugh Cahill, Philip Smallwood, King Wai Yau, Jeremy Nathans

Research output: Contribution to journalArticlepeer-review

Abstract

The bestrophins are a newly described family of anion channels unrelated in primary sequence to any previously characterized channel proteins. The human genome codes for four bestrophins, each of which confers a distinctive plasma membrane conductance on transfected 293 cells. Extracellular treatment with methane-thiosulfonate ethyltrimethylammonium (MTSET) of a series of substitution mutants that eliminate one or more cysteines from human bestrophinl demonstrates that cysteine 69 is the single endogenous cysteine responsible for MTSET inhibition of whole-cell current. Cysteines introduced between positions 78-99 and 223-226 are also accessible to external MTSET, with MTSET modification at positions 79, 80, 83, and 90 producing a 2-6-fold increase in whole-cell current. The latter set of four cysteine-substitution mutants define a region that appears to mediate allosteric control of channel activity. Mapping of transmembrane topography by insertion of N-linked glycosylation sites and tobacco etch virus protease cleavage sites provides evidence for cytosolic N and C termini and an unexpected transmembrane topography with at least three extracellular loops that include positions 60-63, 212-227, and 261-267. These experiments provide the first structural analysis of the bestrophin channel family.

Original languageEnglish (US)
Pages (from-to)41114-41125
Number of pages12
JournalJournal of Biological Chemistry
Volume278
Issue number42
DOIs
StatePublished - Oct 17 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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