Tracking Ca2+ ATPase intermediates in real time by x-ray solution scattering

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DOI

  • Harsha Ravishankar, Umeå University
  • ,
  • Martin Nors Pedersen, European Synchrotron Radiation Facility
  • ,
  • Mattias Eklund
  • ,
  • Aljona Sitsel
  • ,
  • Chenge Li, Stockholm University
  • ,
  • Annette Duelli, Københavns Universitet
  • ,
  • Matteo Levantino, European Synchrotron Radiation Facility, University of Palermo
  • ,
  • Michael Wulff, European Synchrotron Radiation Facility
  • ,
  • Andreas Barth, Stockholm University
  • ,
  • Claus Olesen
  • Poul Nissen
  • Magnus Andersson, Umeå University

Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) transporters regulate calcium signaling by active calcium ion reuptake to internal stores. Structural transitions associated with transport have been characterized by x-ray crystallography, but critical intermediates involved in the accessibility switch across the membrane are missing. We combined time-resolved x-ray solution scattering (TR-XSS) experiments and molecular dynamics (MD) simulations for real-time tracking of concerted SERCA reaction cycle dynamics in the native membrane. The equilibrium [Ca2] E1 state before laser activation differed in the domain arrangement compared with crystal structures, and following laser-induced release of caged ATP, a 1.5-ms intermediate was formed that showed closure of the cytoplasmic domains typical of E1 states with bound Ca2+ and ATP. A subsequent 13-ms transient state showed a previously unresolved actuator (A) domain arrangement that exposed the ADP-binding site after phosphorylation. Hence, the obtained TR-XSS models determine the relative timing of so-far elusive domain rearrangements in a native environment.

OriginalsprogEngelsk
Artikelnummereaaz0981
TidsskriftScience Advances
Vol/bind6
Nummer12
ISSN2375-2548
DOI
StatusUdgivet - mar. 2020

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