Photosynthetic vesicle architecture and constraints on efficient energy harvesting.
Photosynthetic chromatophore vesicles found in some purple bacteria constitute one of the simplest light-harvesting systems in nature. The overall architecture of chromatophore vesicles and the structural integration of vesicle function remain poorly understood despite structural information being available on individual constituent proteins. An all-atom structural model for an entire chromatophore vesicle is presented, which improves upon earlier models by taking into account the stoichiometry of core and antenna complexes determined by the absorption spectrum of intact vesicles in Rhodobacter sphaeroides, as well as the well-established curvature-inducing properties of the dimeric core complex. The absorption spectrum of low-light-adapted vesicles is shown to correspond to a light-harvesting-complex 2 to reaction center ratio of 3:1. A structural model for a vesicle consistent with this stoichiometry is developed and used in the computation of excitonic properties. Considered also is the packing density of antenna and core complexes that is high enough for efficient energy transfer and low enough for quinone diffusion from reaction centers to cytochrome bc(1) complexes.
Sener
Melih
M
Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Strümpfer
Johan
J
Timney
John A
JA
Freiberg
Arvi
A
Hunter
C Neil
CN
Schulten
Klaus
K
D000042:Absorption; D000222:Adaptation, Physiological / Q000528:radiation effects; D020130:Bacterial Chromatophores / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D004734:Energy Metabolism / Q000528:radiation effects; D004735:Energy Transfer / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D010788:Photosynthesis / Q000528:radiation effects; D012242:Rhodobacter sphaeroides / Q000166:cytology* / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D013057:Spectrum Analysis
D045342:Light-Harvesting Protein Complexes