Three-dimensional cryoelectron microscopic reconstruction of the 2.25-MDa homomultimeric phosphoenolpyruvate synthase from Staphylothermus marinus.
The phosphoenolpyruvate synthase (EC 2.7.9.2) of the hyperthermophilic archaeon Staphylothermus marinus forms a 2.25 MDa homomultimeric complex of 24 subunits. Here, computational analysis of low-dose cryoelectron micrographs was used to ascertain that the major rotational symmetry axes were 2-fold, 3-fold, and 4-fold. These symmetry considerations were used to perform a three-dimensional reconstruction to a spatial resolution of 4 nm. This assembly has an octahedral architecture with a solvent accessible interior and with ill-defined yet seemingly flexible appendages on the periphery. This macromolecular assembly is unusually large in mass compared with most other known globular proteins--especially other identified phosphoenolpyruvate synthases which are usually dimeric--and its elaborate quaternary arrangement might represent an adaptation to its extreme environment.
Harauz
G
G
Department of Molecular Biology and Genetics, University of Guelph, Ontario, Canada. gharauz@uoguelph.ca
Li
W
W
D019843:Archaeal Proteins / Q000648:ultrastructure*; D015925:Cryopreservation; D019620:Desulfurococcaceae / Q000201:enzymology*; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D017866:Phosphotransferases (Paired Acceptors) / Q000648:ultrastructure*; D011487:Protein Conformation
D019843:Archaeal Proteins; D046911:Macromolecular Substances; D017866:Phosphotransferases (Paired Acceptors); C022509:pyruvate, water dikinase