Pore architecture of the ORAI1 store-operated calcium channel

Proc Natl Acad Sci U S A. 2010 Mar 16;107(11):4896-901. doi: 10.1073/pnas.1001169107. Epub 2010 Mar 1.

Abstract

ORAI1 is the pore-forming subunit of the calcium release-activated calcium (CRAC) channel, a store-operated channel that is central to Ca(2+) signaling in mammalian cells. Electrophysiological data have shown that the acidic residues E106 in transmembrane helix 1 (TM1) and E190 in TM3 contribute to the high selectivity of ORAI1 channels for Ca(2+). We have examined the pore architecture of the ORAI1 channel using ORAI1 proteins engineered to contain either one or two cysteine residues. Disulfide cross-linking shows that ORAI1 assembles as a tetramer or a higher oligomer with TM1 centrally located. Cysteine side chains projecting from TM1 at position 88, 95, 102, or 106 cross-link efficiently to the corresponding side chain in a second ORAI1 monomer. Cysteine residues at position 190 or at surrounding positions in TM3 do not cross-link. We conclude that E106 residues in wild-type ORAI1 are positioned to form a Ca(2+) binding site in the channel pore and that E190 interacts less directly with ions traversing the pore. The cross-linking data further identify a relatively rigid segment of TM1 adjacent to E106 that is likely to contribute to the selectivity filter.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Biocatalysis / drug effects
  • Calcium Channels / chemistry*
  • Calcium Channels / metabolism
  • Cell Line
  • Cell Membrane / metabolism*
  • Cross-Linking Reagents / pharmacology
  • Cysteine / metabolism
  • Humans
  • Mice
  • Molecular Sequence Data
  • ORAI1 Protein
  • Protein Multimerization / drug effects
  • Protein Structure, Secondary

Substances

  • Calcium Channels
  • Cross-Linking Reagents
  • ORAI1 Protein
  • ORAI1 protein, human
  • Orai1 protein, mouse
  • Cysteine