Subunit Topology of Two 20S Proteasomes from Haloferax volcanii (original) (raw)
Related papers
Structure and structure formation of the 20S proteasome
Molecular biology reports, 1997
Eukaryotic 20S proteasomes are complex oligomeric proteins. The maturation process of the 14 different alpha- and beta-subunits has to occur in a highly coordinate manner. In addition beta-subunits are synthesized as proproteins and correct processing has to be guaranteed during complex maturation. The structure formation can be subdivided in different phases. The knowledge of the individual phases is summarized in this publication. As a first step the newly synthesized monomers have to adopt the correct tertiary structure, a process that might be supported in the case of the beta-subunits by the intramolecular chaperone activity postulated for the prosequences. Subsequently the alpha-subunits form ring-like structures thereby providing docking sites for the different beta-subunits. The result most likely is a double ring structure (13S precursor) representing half-proteasomes, which contain immature proproteins. Two 13S precursors associate to form the proteolytically inactive 16S ...
Biogenesis of eukaryotic 20S proteasomes: the complex maturation pathway of a complex enzyme
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1997
Eukaryotic 20S proteasomes harbor a remarkably complex architecture and unique proteolytic properties. Its catalytic mechanism places this enzyme in a new kind of protease family. The recently solved crystal structure of the yeast 20S complex, along with elucidation of the maturation pathway of human proteasomes, has allowed insight into structure/function relationships. Although not all of the unusual enzymatic properties such as broad substrate specificity, predominant generation of peptides with a specific size, or susceptibility to activating complexes can be explained in detail, knowledge of the structure provides important hints for an explanation of underlying mechanisms. Except for ribosome biogenesis, the complexity of eukaryotic proteasome maturation is without precedence. It is a slow process that involves a series of precisely ordered events. Proteasome structure formation is characterized by an initial cooperative formation of an alpha ring matrix, providing docking sit...
Structural features of archaebacterial and eukaryotic proteasomes
Molecular Biology Reports, 1995
The 26S proteasome is the central protease of the ubiquitin-dependent pathway of protein degradation. The molecule has a molecular mass of approximately 2000 kD and has a highly conserved structure in eukaryotes. The 26S proteasome is formed by a barrel-shaped 20S core complex and two polar 19S complexes. The 20S complex has C2 symmetry and is formed by four seven-membered rings of which the outer rings (c~-type subunits) are rotated by 25.7 ° relative to the inner rings while the inner rings (/3-type subunits) are in register. From a comparison of the activity and regulation of the 26S and 20S particles it can be deduced that the 20S particle contains the protease activity while the 19S complex contains isopeptidase, ATPase and protein unfolding activities. In this article we describe the structures of various proteasome complexes as determined by electron microscopy and discuss structural implications of their subunit sequences.
Journal of Biological Chemistry, 1988
Latent multicatalytic protease complexes, named proteasomes, were purified to apparent homogeneity from various eukaryotic sources, such as human, rat, and chicken liver, Xenopus laevis ovary, and yeast (Saccharomyces cerevisiae), and their functional and structural properties were compared. They showed latency in breakdown of [methyLSH]casein, but were greatly activated in various ways, such as by addition of polylysine. They all degraded three types of fluorogenic oligopeptides at the carboxyl side of basic, neutral, and acidic amino acids, and the three cleavage reactions showed different spectra for inhibition, suggesting that they had three distinct active sites. The proteasomes all seemed to be seryl endopeptidases with similar pH optima in the weakly alkaline region. Their physicochemical properties, such as their sedimentation coefficients (19 S to 22 S) , diffusion coefficients (2.0-2.6 X lo-' cm2 s-'), molecular masses (700-900
The α4 and α7 subunits and assembly of the 20S proteasome
FEBS Letters, 2004
The detailed mechanism of eukaryotic 20S proteasome assembly is currently unknown. In the present study, we demonstrate that the 20S proteasome subunits a4 and a7 interact with each other as well as all the a-subunits in vivo and in vitro. The N-terminal parts of a4 and a7 are essential for these newly discovered interactions in vitro. Glycerol gradient centrifugation of soluble extracts of HEK293 cells and Western blot analyses show that several a-subunits are found in non-proteasomal lowdensity fractions. The a4 and a7 subunits co-immunoprecipitate together from these low-density fractions. The unexpected interaction between a4 and a7 may provide a molecular basis for the formation of previously reported 13S and 16S assembly intermediates.
Late Events in the Assembly of 20S Proteasomes
Journal of Structural Biology, 1998
Electron microscopy and STEM mass measurements have been used to characterize late intermediates in the assembly pathway of wildtype and mutant Rhodococcus proteasomes. A proteolytically inactive and processing-incompetent mutant, K33A, allowed a short-lived late intermediate of the pathway to be captured, the preholoproteasome. In this fully assembled 20S complex the 14 propeptides with an aggregate mass of 100 kDa fill the whole central cavity and most of the two antechambers. It is further shown that in wildtype Rhodococcus proteasomes the propeptides are degraded in a processive manner undergoing multiple cleavages before the products are discharged and the inner cavities are cleared. It appears that the docking of two halfproteasomes, i.e., preholoproteasome formation, is sufficient to trigger autocleavage of the Gly-1/Thr1 bond necessary for active site formation and the subsequent
The complete primary structure of mouse 20S proteasomes
Immunogenetics, 1999
The proteasome is a large multicatalytic proteinase that plays a role in the generation of peptides for presentation by major histocompatibility complex class I molecules. The 20S proteolytic core of mammalian proteasomes is assembled from a group of 17 protein subunits that generate a distinctive pattern of spots upon two-dimensional gel electrophoresis. The genes for most of these subunits have been cloned from humans and rats. We isolated cDNA clones for the mouse orthologues of ten of the subunits [PSMA1 (C2), PSMA2 (C3), PSMA3 (C8), PSMA4 (C9), PSMA5 (ZETA), PSMA6 (IOTA), PSMA7 (C6-I), PSMB2 (C7-I), PSMB3 (C10-II), and PSMB5 (X)] to complete the cloning of all of the mouse subunits. Using antisera raised against these subunits or their orthologues, we verified the identity of these proteins by two-dimensional NEPHGE-PAGE.