Scientific Reports (Nov 2021)

Room temperature XFEL crystallography reveals asymmetry in the vicinity of the two phylloquinones in photosystem I

  • Stephen M. Keable,
  • Adrian Kölsch,
  • Philipp S. Simon,
  • Medhanjali Dasgupta,
  • Ruchira Chatterjee,
  • Senthil Kumar Subramanian,
  • Rana Hussein,
  • Mohamed Ibrahim,
  • In-Sik Kim,
  • Isabel Bogacz,
  • Hiroki Makita,
  • Cindy C. Pham,
  • Franklin D. Fuller,
  • Sheraz Gul,
  • Daniel Paley,
  • Louise Lassalle,
  • Kyle D. Sutherlin,
  • Asmit Bhowmick,
  • Nigel W. Moriarty,
  • Iris D. Young,
  • Johannes P. Blaschke,
  • Casper de Lichtenberg,
  • Petko Chernev,
  • Mun Hon Cheah,
  • Sehan Park,
  • Gisu Park,
  • Jangwoo Kim,
  • Sang Jae Lee,
  • Jaehyun Park,
  • Kensuke Tono,
  • Shigeki Owada,
  • Mark S. Hunter,
  • Alexander Batyuk,
  • Roland Oggenfuss,
  • Mathias Sander,
  • Serhane Zerdane,
  • Dmitry Ozerov,
  • Karol Nass,
  • Henrik Lemke,
  • Roman Mankowsky,
  • Aaron S. Brewster,
  • Johannes Messinger,
  • Nicholas K. Sauter,
  • Vittal K. Yachandra,
  • Junko Yano,
  • Athina Zouni,
  • Jan Kern

DOI
https://doi.org/10.1038/s41598-021-00236-3
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 14

Abstract

Read online

Abstract Photosystem I (PS I) has a symmetric structure with two highly similar branches of pigments at the center that are involved in electron transfer, but shows very different efficiency along the two branches. We have determined the structure of cyanobacterial PS I at room temperature (RT) using femtosecond X-ray pulses from an X-ray free electron laser (XFEL) that shows a clear expansion of the entire protein complex in the direction of the membrane plane, when compared to previous cryogenic structures. This trend was observed by complementary datasets taken at multiple XFEL beamlines. In the RT structure of PS I, we also observe conformational differences between the two branches in the reaction center around the secondary electron acceptors A1A and A1B. The π-stacked Phe residues are rotated with a more parallel orientation in the A-branch and an almost perpendicular confirmation in the B-branch, and the symmetry breaking PsaB-Trp673 is tilted and further away from A1A. These changes increase the asymmetry between the branches and may provide insights into the preferential directionality of electron transfer.