CaltechAUTHORS
Published December 31, 2024 | Submitted v1
Working Paper Open

Application of amber suppression to study the role of Tyr M210 in electron transfer in R. sphaeroides photosynthetic reaction centers

Tran, Khoi1 ORCID icon
Faries, Kaitlyn2
Magdaong, Nikki2 ORCID icon
Mathews, Irimpan3
Weaver, Jared1
Kirsh, Jacob4 ORCID icon
Holten, Dewey2
Kirmaier, Christine2 ORCID icon
Boxer, Steven1 ORCID icon
  • 1. ROR icon Stanford University
  • 2. ROR icon Washington University in St. Louis
  • 3. ROR icon SLAC National Accelerator Laboratory
  • 4. ROR icon California Institute of Technology
An error occurred while generating the citation.

Abstract

The initial light-induced electron transfer (ET) steps in the bacterial photosynthetic reaction center (RC) have been extensively studied and provide a paradigm for connecting structure and function. Although RCs have local pseudo-C2 symmetry, ET only occurs along the A branch of chromophores. Tyrosine M210 is a key symmetry-breaking residue adjacent to bacteriochlorophyll BA that bridges primary electron donor P and bacteriopheophytin acceptor HA. We used amber suppression to incorporate phenylalanine variants with different electron-withdrawing/donating capabilities at position M210. X-ray data generally reveal no appreciable structural changes due to the mutations. P* decay and P+HA formation are multi-exponential (~2-9, ~10-60, and ~100-300 ps) and temperature dependent. The 1020 nm transient-absorption band of P+BA is barely resolved for a few variants at 295 K and for none at 77 K. The results indicate a change from two-step ET for wild-type RCs to dominance of one-step superexchange ET for the mutants. Resonance Stark spectroscopy reveals that the free energy of P+BA changes by -57 to +66 meV among the phenylalanine variants. Because P+BA apparently lies above P* in all phenylalanine variants, the perturbations primarily affect the energy denominator for superexchange mixing. The findings deepen insight into primary ET in the bacterial RC.

Copyright and License

The content is available under CC BY NC ND 4.0
 

Acknowledgement

This work was supported by a grant from the NSF Biophysics Program to S.G.B. (MCB-1915727). K.M.F, N. M., D.H. and C.K. were supported by a grant from the U. S. Department of Energy, Office of Basic Energy Sciences (DE-CD0002036). We thank the Vincent Coates Foundation Mass Spectrometry Laboratory, Stanford University Mass Spectrometry and particularly Theresa Laughlin for their support in performing the LC–MS in this study. This work was supported by NIH Grant GM118044 (to S.G.B.). Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DEAC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research, and by the National Institutes of Health, National Institute of General Medical Sciences (P30GM133894). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH.

Supplemental Material

Supporting Information describing methodology and background information

Files

application-of-amber-suppression-to-study-the-role-of-tyr-m210-in-electron-transfer-in-r-sphaeroides-photosynthetic-reaction-centers.pdf

Additional details

Funding Caltech Custom Metadata
Created:
March 10, 2025
Modified:
March 10, 2025