Protein-induced membrane curvature investigated through molecular dynamics flexible fitting.
In the photosynthetic purple bacterium Rhodobacter (Rba.) sphaeroides, light is absorbed by membrane-bound light-harvesting (LH) proteins LH1 and LH2. LH1 directly surrounds the reaction center (RC) and, together with PufX, forms a dimeric (RC-LH1-PufX)2 protein complex. In LH2-deficient Rba. sphaeroides mutants, RC-LH1-PufX dimers aggregate into tubular vesicles with a radius of approximately 250-550 A, making RC-LH1-PufX one of the few integral membrane proteins known to actively induce membrane curvature. Recently, a three-dimensional electron microscopy density map showed that the Rba. sphaeroides RC-LH1-PufX dimer exhibits a prominent bend at its dimerizing interface. To investigate the curvature properties of this highly bent protein, we employed molecular dynamics simulations to fit an all-atom structural model of the RC-LH1-PufX dimer within the electron microscopy density map. The simulations reveal how the dimer produces a membrane with high local curvature, even though the location of PufX cannot yet be determined uniquely. The resulting membrane curvature agrees well with the size of RC-LH1-PufX tubular vesicles, and demonstrates how the local curvature properties of the RC-LH1-PufX dimer propagate to form the observed long-range organization of the Rba. sphaeroides tubular vesicles.
Hsin
Jen
J
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Gumbart
James
J
Trabuco
Leonardo G
LG
Villa
Elizabeth
E
Qian
Pu
P
Hunter
C Neil
CN
Schulten
Klaus
K
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D002856:Chromatophores / Q000737:chemistry; D003198:Computer Simulation; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008854:Microscopy, Electron; D008958:Models, Molecular; D008962:Models, Theoretical; D055503:Protein Multimerization; D012242:Rhodobacter sphaeroides / Q000737:chemistry* / Q000648:ultrastructure; D014741:Video Recording
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; C088749:PufX protein, Rhodobacter; C094744:light-harvesting complex 1, Rhodospirillum