Identification of macromolecular complexes in cryoelectron tomograms of phantom cells.
Electron tomograms of intact frozen-hydrated cells are essentially three-dimensional images of the entire proteome of the cell, and they depict the whole network of macromolecular interactions. However, this information is not easily accessible because of the poor signal-to-noise ratio of the tomograms and the crowded nature of the cytoplasm. Here, we describe a template matching algorithm that is capable of detecting and identifying macromolecules in tomographic volumes in a fully automated manner. The algorithm is based on nonlinear cross correlation and incorporates elements of multivariate statistical analysis. Phantom cells, i.e., lipid vesicles filled with macromolecules, provide a realistic experimental scenario for an assessment of the fidelity of this approach. At the current resolution of approximately 4 nm, macromolecules in the size range of 0.5-1 MDa can be identified with good fidelity.
Frangakis
Achilleas S
AS
Max-Planck-Institut für Biochemie, Molekulare Strukturbiologie, Am Klopferspitz 18a, 82152 Martinsried, Germany. frangak@biochem.mpg.de
Böhm
Jochen
J
Förster
Friedrich
F
Nickell
Stephan
S
Nicastro
Daniela
D
Typke
Dieter
D
Hegerl
Reiner
R
Baumeister
Wolfgang
W
D000465:Algorithms; D019843:Archaeal Proteins / Q000032:analysis*; D018833:Chaperonins / Q000032:analysis*; D018699:Coated Vesicles; D020285:Cryoelectron Microscopy / Q000379:methods; D003546:Cysteine Endopeptidases / Q000032:analysis*; D008081:Liposomes / Q000737:chemistry; D009097:Multienzyme Complexes / Q000032:analysis*; D015999:Multivariate Analysis; D017711:Nonlinear Dynamics; D046988:Proteasome Endopeptidase Complex
D019843:Archaeal Proteins; D008081:Liposomes; D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D018833:Chaperonins