Non-cryogenic structure of a chloride pump provides crucial clues to temperature-dependent channel transport efficiency Academic Article uri icon


  • Non-cryogenic protein structures determined at ambient temperature may disclose significant information about protein activity. Chloride-pumping rhodopsin (ClR) exhibits a trend to hyperactivity induced by a change in the photoreaction rate because of a gradual decrease in temperature. Here, to track the structural changes that explain the differences in CIR activity resulting from these temperature changes, we used serial femtosecond crystallography (SFX) with an X-ray free electron laser (XFEL) to determine the non-cryogenic structure of ClR at a resolution of 1.85 Å, and compared this structure with a cryogenic ClR structure obtained with synchrotron X-ray crystallography. The XFEL-derived ClR structure revealed that the all-trans retinal (ATR) region and positions of two coordinated chloride ions slightly differed from those of the synchrotron-derived structure. Moreover, the XFEL structure enabled identification of one additional water molecule forming a hydrogen bond network with a chloride ion. Analysis of the channel cavity and a difference distance matrix plot (DDMP) clearly revealed additional structural differences. B-factor information obtained from the non-cryogenic structure supported a motility change on the residual main and side chains as well as of chloride and water molecules because of temperature effects. Our results indicate that non-cryogenic structures and time-resolved XFEL experiments could contribute to a better understanding of the chloride-pumping mechanism of ClR and other ion pumps.


  • Yun, Ji-Hye
  • Li, Xuanxuan
  • Park, Jae-Hyun
  • Wang, Yang
  • Ohki, Mio
  • Jin, Zeyu
  • Lee, Wonbin
  • Park, Sam-Yong
  • Hu, Hao
  • Li, Chufeng
  • Zatsepin, Nadia
  • Hunter, Mark S
  • Sierra, Raymond G
  • Koralek, Jake
  • Yoon, Chun Hong
  • Cho, Hyun-Soo
  • Weierstall, Uwe
  • Tang, Leihan
  • Liu, Haiguang
  • Lee, Weontae

publication date

  • January 18, 2019