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Cell Feb 1998
Review
Topics: Animals; Cell Compartmentation; Cysteine Endopeptidases; Humans; Models, Molecular; Multienzyme Complexes; Proteasome Endopeptidase Complex; Protein Conformation
PubMed: 9476896
DOI: 10.1016/s0092-8674(00)80929-0 -
The Journal of Biological Chemistry Nov 1995The multicatalytic and multisubunit proteasomal complexes have been implicated in the processing of antigens to peptides presented by class I major histocompatibility...
The multicatalytic and multisubunit proteasomal complexes have been implicated in the processing of antigens to peptides presented by class I major histocompatibility complex molecules. Two structural complexes of this proteinase, 20 S and 26 S proteasomes, have been isolated from cells. By analyzing in vivo assembly of the proteasomal complexes we show that the 20 S proteasomal complexes are irreversibly assembled via 15 S assembly intermediates containing unprocessed beta-type subunits. The 20 S proteasomes further associate reversibly with proteasome activators PA28 or pre-existing ATPase complexes to form 26 S proteasomal complexes. Our findings that not all of the 20 S proteasomal complexes are assembled into 26 S proteasomal complexes within cells and that all of PA28 and ATPase complexes are associated with 20 S proteasomes strongly suggest that all proteasomal complexes coexist within cells. We further demonstrate that 26 S proteasomal complexes are predominantly present in the cytoplasm and a significant portion of the 20 S proteasomal complexes is associated with the endoplasmic reticulum membrane. Taken together, our findings suggest that depending upon their associated regulatory components, 26 S and 20 S-PA28 proteasomal complexes serve different housekeeping functions within the cells, while they degrade antigens in a cooperative manner in antigen processing.
Topics: Animals; Antigens; Cell Line; Cysteine Endopeptidases; Endoplasmic Reticulum; Humans; Lymphoma; Macromolecular Substances; Major Histocompatibility Complex; Mice; Models, Structural; Multienzyme Complexes; Phosphates; Phosphorylation; Proteasome Endopeptidase Complex; Protein Biosynthesis; Protein Processing, Post-Translational; Recombinant Proteins; Transfection; Tumor Cells, Cultured
PubMed: 7499235
DOI: 10.1074/jbc.270.46.27687 -
Chembiochem : a European Journal of... Sep 2019Advanced glycation end products (AGEs) are a heterogeneous group of molecules that emerge from the condensation of sugars and proteins through the Maillard reaction....
Advanced glycation end products (AGEs) are a heterogeneous group of molecules that emerge from the condensation of sugars and proteins through the Maillard reaction. Despite a significant number of studies showing strong associations between AGEs and the pathologies of aging-related illnesses, it has been a challenge to establish AGEs as causal agents primarily due to the lack of tools in reversing AGE modifications at the molecular level. Herein, we show that MnmC, an enzyme involved in a bacterial tRNA-modification pathway, is capable of reversing the AGEs carboxyethyl-lysine (CEL) and carboxymethyl-lysine (CML) back to their native lysine structure. Combining structural homology analysis, site-directed mutagenesis, and protein domain dissection studies, we generated a variant of MnmC with improved catalytic properties against CEL in its free amino acid form. We show that this enzyme variant is also active on a CEL-modified peptidomimetic and an AGE-containing peptide that has been established as an authentic ligand of the receptor for AGEs (RAGE). Our data demonstrate that MnmC variants are promising lead catalysts toward the development of AGE-reversal tools and a better understanding of AGE biology.
Topics: Biocatalysis; Escherichia coli; Escherichia coli Proteins; Glycation End Products, Advanced; Kinetics; Lysine; Multienzyme Complexes; Mutation; Protein Engineering; Substrate Specificity
PubMed: 31013547
DOI: 10.1002/cbic.201900158 -
Proceedings of the National Academy of... May 2018Viruses are remarkable nanomachines that efficiently hijack cellular functions to replicate and self-assemble their components within a complex biological environment....
Viruses are remarkable nanomachines that efficiently hijack cellular functions to replicate and self-assemble their components within a complex biological environment. As all steps of the viral life cycle depend on formation of a protective proteinaceous shell that packages the DNA or RNA genome, bottom-up construction of virus-like nucleocapsids from nonviral materials could provide valuable insights into virion assembly and evolution. Such constructs could also serve as safe alternatives to natural viruses for diverse nano- and biotechnological applications. Here we show that artificial virus-like nucleocapsids can be generated-rapidly and surprisingly easily-by engineering and laboratory evolution of a nonviral protein cage formed by lumazine synthase (AaLS) and its encoding mRNA. Cationic peptides were appended to the engineered capsid proteins to enable specific recognition of packaging signals on cognate mRNAs, and subsequent evolutionary optimization afforded nucleocapsids with expanded spherical structures that encapsulate their own full-length RNA genome in vivo and protect the cargo molecules from nucleases. These findings provide strong experimental support for the hypothesis that subcellular protein-bounded compartments may have facilitated the emergence of ancient viruses.
Topics: Bacteria; Bioengineering; Capsid Proteins; Directed Molecular Evolution; Models, Molecular; Multienzyme Complexes; Nucleocapsid; Peptide Fragments; Virus Assembly
PubMed: 29735682
DOI: 10.1073/pnas.1800527115 -
Bioorganic Chemistry Jun 2005Thiamin diphosphate (ThDP), the vitamin B1 coenzyme, is an excellent representative of coenzymes, which carry out electrophilic catalysis by forming a covalent complex... (Review)
Review
Thiamin diphosphate (ThDP), the vitamin B1 coenzyme, is an excellent representative of coenzymes, which carry out electrophilic catalysis by forming a covalent complex with their substrates. The function of ThDP is to greatly increase the acidity of two carbon acids by stabilizing their conjugate bases, the ylide/C2-carbanion of the thiazolium ring and the C2alpha-carbanion (or enamine) once the substrate binds to ThDP. In recent years, several ThDP-bound intermediates on such pathways have been characterized by both solution and solid-state (X-ray) methods. Prominent among these advances are X-ray crystallographic results identifying both oxidative and non-oxidative intermediates, rapid chemical quench followed by NMR detection of a several intermediates which are stable under acidic conditions, and circular dichroism detection of the 1',4'-imino tautomer of ThDP in some of the intermediates. Some of these methods also enable the investigator to determine the rate-limiting step in the complex series of steps.
Topics: Coenzymes; Crystallography, X-Ray; Enzymes; Models, Molecular; Molecular Structure; Multienzyme Complexes; Substrate Specificity; Thiamine Pyrophosphate
PubMed: 15888311
DOI: 10.1016/j.bioorg.2005.02.001 -
Progress in Biophysics and Molecular... 1989
Review
Topics: Animals; Cytosol; Kinetics; Mitochondria; Multienzyme Complexes
PubMed: 2692072
DOI: 10.1016/0079-6107(89)90016-3 -
Molecular Microbiology Sep 2006The exosome, a large multisubunit complex with exoribonucleic activity, emerges as the central 3' RNA degradation and processing factor in eukaryotes and archaea. But... (Review)
Review
The exosome, a large multisubunit complex with exoribonucleic activity, emerges as the central 3' RNA degradation and processing factor in eukaryotes and archaea. But how are the many RNA substrates of the exosome degraded in a processive, yet controlled manner? Recent functional and structural progress shows that the exosome is a macromolecular cage, where the nuclease active sites are situated in a central processing chamber. A narrow entry pore controls access to the active sites in the processing chamber and prevents uncontrolled RNA decay. The emerging mechanism of exosome function suggests a strikingly parallel architectural concept to protein degradation by proteasomes.
Topics: Archaea; Exoribonucleases; Multienzyme Complexes; Proteasome Endopeptidase Complex; Protein Conformation; RNA; Yeasts
PubMed: 16968219
DOI: 10.1111/j.1365-2958.2006.05331.x -
ELife Nov 2016Respirasomes are macromolecular assemblies of the respiratory chain complexes I, III and IV in the inner mitochondrial membrane. We determined the structure of...
Respirasomes are macromolecular assemblies of the respiratory chain complexes I, III and IV in the inner mitochondrial membrane. We determined the structure of supercomplex IIIIIV from bovine heart mitochondria by cryo-EM at 9 Å resolution. Most protein-protein contacts between complex I, III and IV in the membrane are mediated by supernumerary subunits. Of the two Rieske iron-sulfur cluster domains in the complex III dimer, one is resolved, indicating that this domain is immobile and unable to transfer electrons. The central position of the active complex III monomer between complex I and IV in the respirasome is optimal for accepting reduced quinone from complex I over a short diffusion distance of 11 nm, and delivering reduced cytochrome to complex IV. The functional asymmetry of complex III provides strong evidence for directed electron flow from complex I to complex IV through the active complex III monomer in the mammalian supercomplex.
Topics: Animals; Cattle; Cryoelectron Microscopy; Electron Transport; Mitochondria; Multienzyme Complexes; Myocardium
PubMed: 27830641
DOI: 10.7554/eLife.21290 -
Dalton Transactions (Cambridge, England... Apr 2011Numerous metalloproteins are important therapeutic targets that are gaining increased attention in the medicinal and bioinorganic chemistry communities. This Perspective... (Review)
Review
Numerous metalloproteins are important therapeutic targets that are gaining increased attention in the medicinal and bioinorganic chemistry communities. This Perspective article describes some emerging trends and recent findings in the area of metalloprotein inhibitor discovery and development. In particular, increasing recognition of the importance of the metal-ligand interactions in these systems calls for more input and consideration from the bioinorganic community to address questions traditionally confined to the medicinal chemistry community.
Topics: Aldose-Ketose Isomerases; Aminopeptidases; Animals; Drug Discovery; Enzyme Inhibitors; Humans; Metalloproteins; Methionyl Aminopeptidases; Multienzyme Complexes; Oxidoreductases; Prodrugs
PubMed: 21290034
DOI: 10.1039/c0dt01743d -
The Journal of Biological Chemistry Sep 1982Using a three-step procedure designed to minimize the risks of proteolysis, high molecular weight complexes containing the same seven aminoacyl-tRNA synthetases specific... (Comparative Study)
Comparative Study
Using a three-step procedure designed to minimize the risks of proteolysis, high molecular weight complexes containing the same seven aminoacyl-tRNA synthetases specific for isoleucine, leucine, methionine, lysine, arginine, glutamic acid, and glutamine were purified from sheep liver and spleen, as well as from rabbit reticulocytes and liver. The polypeptide composition of these complexes, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is characteristic of the animal species from which they are derived. The complexes from sheep liver and spleen display indistinguishable polypeptide patterns composed of 11 major components. Of the 10 common components which characterize the complexes of rabbit reticulocytes and liver, 4 are also shared by the complexes from sheep, while 6 have distinctly different electrophoretic mobilities. Furthermore, in the case of the complex from rabbit reticulocytes, it is shown that the enzyme and polypeptide composition of the complex is independent of the purification method employed. The isolation of high molecular weight complexes of identical aminoacyl-tRNA synthetase and polypeptide compositions from two cell types as radically different as rabbit reticulocytes and hepatocytes suggests that these multienzyme complexes do not arise as artifacts of preparation and supports the view that they reflect a structural organization existing within the cell.
Topics: Amino Acyl-tRNA Synthetases; Animals; Liver; Methionine-tRNA Ligase; Multienzyme Complexes; Rabbits; Reticulocytes; Sheep; Species Specificity
PubMed: 7107644
DOI: No ID Found