title: Structural model and excitonic properties of the dimeric RC-LH1-PufX complex from Rhodobacter sphaeroides.
abstract: The light-harvesting apparatus of the purple bacterial photosynthetic unit consists of a pool of peripheral light-harvesting complexes that transfer excitation energy to a reaction center (RC) via the surrounding pigment-protein complex LH1. Recent electron microscopy and atomic force microscopy studies have revealed that RC-LH1 units of Rhodobacter sphaeroides form membrane-bending dimeric complexes together with the polypeptide PufX. We present a structural model for these RC-LH1-PufX dimeric complexes constructed using the molecular dynamics flexible fitting method based on an EM density map. The arrangement of the LH1 BChls displays a distortion near the proposed location of the PufX polypeptide. The resulting atomic model for BChl arrays is used to compute the excitonic properties of the dimeric RC-LH1 complex. A comparison is presented between the structural and excitonic features of the S-shaped dimeric BChl array of Rhodobacter sphaeroides and the circular BChl arrangement found in other purple bacteria.
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
authors.forename: Melih
authors.initials: M
authors.lastname: Sener
authors.forename: Jen
authors.initials: J
authors.lastname: Hsin
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Trabuco
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Villa
authors.forename: Pu
authors.initials: P
authors.lastname: Qian
authors.forename: C Neil
authors.initials: CN
authors.lastname: Hunter
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten