Wolfgang Baumeister

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In eukaryotic cells, most proteins in the cytosol and nucleus are degraded via the ubiquitin-proteasome pathway. The 26S proteasome is a 2.5-MDa molecular machine built from approximately 31 different subunits, which catalyzes protein degradation. It contains a barrel-shaped proteolytic core complex (the 20S proteasome), capped at one or both ends by 19S(More)
The three-dimensional structure of the proteasome from the archaebacterium Thermoplasma acidophilum has been elucidated by x-ray crystallographic analysis by means of isomorphous replacement and cyclic averaging. The atomic model was built and refined to a crystallographic R factor of 22.1 percent. The 673-kilodalton protease complex consists of 14 copies(More)
The proteasome consists of a 20S proteolytic core particle (CP) and a 19S regulatory particle (RP), which selects ubiquitinated substrates for translocation into the CP. An eight-subunit subcomplex of the RP, the lid, can be dissociated from proteasomes prepared from a deletion mutant for Rpn10, an RP subunit. A second subcomplex, the base, contains all six(More)
An adaptation of the 'correlation averaging' method is described which allows reliable and almost fully automatic image averaging in the case of near-periodic structures notwithstanding the presence of substantial crystal imperfections; methods for assessing resolution and symmetry without reliance on crystallinity are also discussed. Electron micrographs(More)
Protein degradation is a necessity for many reasons: three domains of life: archaea, bacteria, and eukarya. Homeostasis must be maintained while cellular strucThis bears testimony to an old evolutionary principle. In tures are continually rebuilt, inparticular during developfact, contrary to organelles such as the lysosome, selfment or in response to(More)
Crista junctions (CJs) are important for mitochondrial organization and function, but the molecular basis of their formation and architecture is obscure. We have identified and characterized a mitochondrial membrane protein in yeast, Fcj1 (formation of CJ protein 1), which is specifically enriched in CJs. Cells lacking Fcj1 lack CJs, exhibit concentric(More)
Nuclear pore complexes (NPCs) are gateways for nucleocytoplasmic exchange. To analyze their structure in a close-to-life state, we studied transport-active, intact nuclei from Dictyostelium discoideum by means of cryoelectron tomography. Subvolumes of the tomograms containing individual NPCs were extracted in silico and subjected to three-dimensional(More)
Electron tomography (ET) is uniquely suited to obtain three-dimensional reconstructions of pleomorphic structures, such as cells, organelles or supramolecular assemblies. Although the principles of ET have been known for decades, its use has gathered momentum only in recent years, thanks to technological advances and its combination with improved specimen(More)
Thermoplasma acidophilum is a thermoacidophilic archaeon that thrives at 59 degrees C and pH 2, which was isolated from self-heating coal refuse piles and solfatara fields. Species of the genus Thermoplasma do not possess a rigid cell wall, but are only delimited by a plasma membrane. Many macromolecular assemblies from Thermoplasma, primarily proteases and(More)
The mechanism of GroEL (chaperonin)-mediated protein folding is only partially understood. We have analysed structural and functional properties of the interaction between GroEL and the co-chaperonin GroES. The stoichiometry of the GroEL 14mer and the GroES 7mer in the functional holo-chaperonin is 1:1. GroES protects half of the GroEL subunits from(More)