English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Stim and Orai proteins comprise the molecular machinery of Ca(2+) release-activated Ca(2+) (CRAC) channels. As an approach toward understanding the gating of Orai1 channels, we investigated effects of selected mutations at two conserved sites in the first transmembrane segment (TM1): arginine 91 located near the cytosolic end of TM1 and glycine 98 near the middle of TM1. Orai1 R91C, when coexpressed with STIM1, was activated normally by Ca(2+)-store depletion. Treatment with diamide, a thiol-oxidizing agent, induced formation of disulfide bonds between R91C residues in adjacent Orai1 subunits and rapidly blocked STIM1-operated Ca(2+) current. Diamide-induced blocking was reversed by disulfide bond-reducing agents. These results indicate that R91 forms a very narrow part of the conducting pore at the cytosolic side. Alanine replacement at G98 prevented STIM1-induced channel activity. Interestingly, mutation to aspartate (G98D) or proline (G98P) caused constitutive channel activation in a STIM1-independent manner. Both Orai1 G98 mutants formed a nonselective Ca(2+)-permeable conductance that was relatively resistant to block by Gd(3+). The double mutant R91W/G98D was also constitutively active, overcoming the normal inhibition of channel activity by tryptophan at the 91 position found in some patients with severe combined immunodeficiency (SCID), and the double mutant R91C/G98D was resistant to diamide block. These data suggest that the channel pore is widened and ion selectivity is altered by mutations at the G98 site that may perturb α-helical structure. We propose distinct functional roles for G98 as a gating hinge and R91 as part of the physical gate at the narrow inner mouth of the channel.

Mutations in Orai1 transmembrane segment 1 cause STIM1-independent activation of Orai1 channels at glycine 98 and channel closure at arginine 91