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Title: High yield of secondary B-side electron transfer in mutant Rhodobacter capsulatus reaction centers

From the crystal structures of reaction centers (RCs) from purple photosynthetic bacteria, two pathways for electron transfer (ET) are apparent but only one pathway (the A side) operates in the native protein-cofactor complex. Partial activation of the B-side pathway has unveiled the true inefficiencies of ET processes on that side in comparison to analogous reactions on the A side. Of significance are the relative rate constants for forward ET and the competing charge recombination reactions. On the B side, these rate constants are nearly equal for the secondary charge-separation step (ET from bacteriopheophytin to quinone), relegating the yield of this process to < 50%. Herein we report efforts to optimize this step. In surveying all possible residues at position 131 in the M subunit, we discovered that when glutamic acid replaces the native valine the efficiency of the secondary ET is nearly two-fold higher than in the wild-type RC. The positive effect of M131 Glu is likely due to formation of a hydrogen bond with the ring V keto group of the B-side bacteriopheophytin leading to stabilization of the charge-separated state involving this cofactor. In conclusion, this change slows charge recombination by roughly a factor of two and affords themore » improved yield of the desired forward ET to the B-side quinone terminal acceptor.« less
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  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Washington Univ., St. Louis, MO (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; FG02-09ER16116; DGE-1143954; FG-02-09ER16116
Published Article
Journal Name:
Biochimica et Biophysica Acta - Bioenergetics
Additional Journal Information:
Journal Volume: 1837; Journal Issue: 11; Related Information: Open Archive; Journal ID: ISSN 0005-2728
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; photosynthetic reaction center; charge recombination; high-throughput screening; ultrafast spectroscopy; directed evolution; transmembrane electron transfer
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1222397; OSTI ID: 1225368