title: Overall energy conversion efficiency of a photosynthetic vesicle.
abstract: The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytb⁢c1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%-5% of full sunlight is calculated to be 0.12-0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.
authors: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.|Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States.
authors: Melih
authors: M
authors: Sener
authors: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.|Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, United States.
authors: Johan
authors: J
authors: Strumpfer
authors: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.
authors: Abhishek
authors: A
authors: Singharoy
authors: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom.
authors: C Neil
authors: CN
authors: Hunter
authors: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.|Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States.|Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, United States.
authors: Klaus
authors: 0000-0001-7192-9632
authors: K
authors: Schulten
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D020130:Bacterial Chromatophores / Q000378:metabolism* / Q000528:radiation effects*; D004734:Energy Metabolism; D006873:Hydroquinones / Q000032:analysis; D008027:Light; D011809:Quinones / Q000032:analysis; D012242:Rhodobacter sphaeroides / Q000378:metabolism* / Q000528:radiation effects*
chemical_list: D006873:Hydroquinones; D011809:Quinones; D000255:Adenosine Triphosphate
keywords: ATP production; Rhodobacter sphaeroides; bacterial photosynthesis; biophysics; computational biology; energy conversion efficiency; excitation transfer; structural biology; systems biology