Thermosomes and Proteasomes:
Evolution of the Cellular Protein Folding and Degradation Machinery
Baumeister, W.
Max-Planck-Institut für Biochemie, D-82152 Martinsried b. München, Germany
Hsp60 proteins or chaperonins represent a distinct family of molecular chaperones, which assist in the folding of newly synthesized or the refolding of stress-denatured proteins. In archaea, the chaperonin/hsp 60 family is represented by the thermosomes [1,2]. They are closely related to the eukaryotic cytosolic chaperonin TRiC/CCT [3]. Both form ring-shaped hexadacameric complexes built from 1-2 (thermosomes) or 8 (TRiC/CCT) distinct but related subunits. The structure of the thermosome from Thermoplasma was recently determined by a combined election microscopy/X-ray crystallography approach [4,5].
Intracellular protein degradation is essential for the maintenance of homeostasis, it serves to remove abnormal, that is, misfolded proteins and it is a critical element of many regulatory mechanisms. A large (2 MDa) ATP-dependent proteolytic complex which is ubiquitous in eukaryotic cells performs these tasks. A key feature of the proteasome is the 'self-compartmentalization' of the proteolytic reaction, i.e. its confinement to an inner nanocompartment [6]. A related but simpler proteasome appears to occur in all archaea. Because of its relative simplicity, the Thermoplasma proteasome has taken a pivotal role in elucadating the structure and enzymatic mechanism of the poteolytic machinery [7,8,9].
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[9] W. Baumeister, Z. Cjeka, M. Kania, E. Seemüller (1997) Biol. Chem. 378, 121-130
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Tuesday, April 7 |
04:50 pm |