title: The 1.5-nm projection structure of HeLa cell prosome-MCP (proteasome) provided by two-dimensional crystals.
abstract: We grew two-dimensional crystals of HeLa cell prosomes, also called multicatalytic proteinases (MCP) and proteasomes, for a structure determination by electron microscopy. The molecules were arranged in side views in these crystals. The crystals have p21 plane group symmetry with one particle per unit cell. This symmetry confirms previously published evidence indicating that eukaryotic prosome-MCPs are dimers of two identical halves. Structure factors from six crystals each comprising more than 1000 unit cells were combined to generate a 1.5-nm projection map. We discovered that while the general cylindrical shape of HeLa prosome-MCPs resembles the shape of the archaebacterial Thermoplasma acidophilum proteasomes, the internal structure differs significantly. We propose that because of different subunit composition, the architecture of HeLa prosome-MCPs differs from the basic architecture of related particles previously reported.
authors.affiliation: Groningen Biomolecular Science, University of Groningen, The Netherlands.
authors.forename: G A
authors.initials: GA
authors.lastname: Perkins
authors.forename: W
authors.initials: W
authors.lastname: Bergsma-Schutter
authors.forename: W
authors.initials: W
authors.lastname: Keegstra
authors.forename: A C
authors.initials: AC
authors.lastname: Arnberg
authors.forename: O
authors.initials: O
authors.lastname: Coux
authors.forename: K
authors.initials: K
authors.lastname: Scherrer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D006367:HeLa Cells / Q000201:enzymology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D015999:Multivariate Analysis; D009363:Neoplasm Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000648:ultrastructure; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D013822:Thermoplasma / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex