Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated three aspects of nucleotide usage by the 26S proteasome and its regulatory complex (RC). Both particles hydrolyze the four major ribonucleotides, but ATP and CTP have substantially lower Kms for hydrolysis than do GTP and UTP. The Km for ATP hydrolysis is 15 microm for the 26S proteasome and 30 microm for the regulatory complex. Formation of the 26S proteasome from the RC and the 20S proteasome requires about 5 microm ATP. Although measurable degradation of Ubiquitin(Ub)-lysozyme conjugates occurs in the presence of CTP, GTP, and UTP, the best nucleotide for Ub-conjugate degradation by the 26S proteasome is ATP, with an estimated Km of 12 microm. In summary, our studies show that micromolar concentrations of ATP are sufficient for several 26S proteasome activities.
...
PMID:Effects of nucleotides on assembly of the 26S proteasome and degradation of ubiquitin conjugates. 922 75

The title compound Ta6Br(2+)12 is of interest for the analysis of biological structures as a heavy-metal derivative with great potential for the structure determination of large protein systems. In macromolecular crystallography the phases of the measured structure factor amplitudes have to be determined. The most widely used method for novel structures is isomorphous replacement by introducing electron-rich compounds into the protein crystals. These compounds produce measurable changes of the diffraction intensities, which allow phase determination. We synthetized the Ta6Br(2+)12 cluster in high yields, crystallized it, and determined its crystal structure by X-ray diffraction analysis at atomic resolution. The cluster is a regular octahedron consisting of six metal atoms with 12 bridging bromine atoms along the 12 edges of the octahedron. The cluster is compact, of approximately spherical shape with about 4.3 A radius and highly symmetrical. One Ta6Br(2+)12 ion adds 856 electrons to a protein, a considerable contribution to the scattering power even of large proteins or multimeric systems. At low resolution all atoms of the cluster scatter in phase and act as a super heavy-atom, which is easy to locate in the difference Patterson map. We investigated its binding sites in the biologically significant high-resolution structures of an antibody V(L) domain, dimethyl sulfoxide reductase, GTP-cyclohydrolase I, and the proteasome. With the randomly oriented cluster, treated as a single site scatterer, phases could be used only up to 6 A resolution. In contrast, when the cluster is correctly oriented, phases calculated from its 18 atom sites can be used to high resolution. We present the atomic structure of the Ta6Br(2+)12, describe a method to determine its localization and orientation in the unit cell of protein crystals of two different proteins, and analyse its phasing power. We show that phases can be calculated to high resolution. The phase error is lower by more than 30 degrees compared to the single site approximation, using a resolution of 2.2 A. Furthermore, Ta6Br(2+)12 has two different strong anomalous scatterers tantalum and bromine to be used for phase determination.
...
PMID:Ta6Br(2+)12, a tool for phase determination of large biological assemblies by X-ray crystallography. 923 95

SUG1 is an integral component of the 26 S proteasome. Belonging to a novel putative ATPase family, it shares four conserved motifs characteristic of ATP-dependent DNA/RNA helicases. Recombinant rat SUG1 (rSUG1) produced in Escherichia coli was highly purified and characterized in terms of its biochemical properties. The rSUG1 exhibited a Mg2+-dependent ATPase activity. The Km for ATP and Vmax of rSUG1 were 35 microM and 7 pmol of ATP/min/microg of protein, respectively. Both ATPase activity to release [32P]monophosphate and [32P]ATP-labeling activity were coordinately affected by cold ATP severely, GTP and UTP moderately, and CTP little. Interestingly, the rSUG1 ATPase activity was stimulated by poly(U) and poly(C), but not by poly(A), poly(G), or by any forms of DNAs tested. A UV cross-linking assay also indicated poly(U)- and poly(C)-stimulated labeling of rSUG1 with [alpha-32P]ATP. Moreover, the ATPase activity was facilitated by cellular poly(A)+ RNA, but not by poly(A)- RNA. RNA transcribed in vitro from cDNA encoding a b-Zip protein could stimulate the ATPase activity. This is the first report to demonstrate a specific RNA requirement for ATPase with respect to the proteasomal ATPases. Our present work suggests that SUG1 can specifically interact with protein-coding RNA (mRNA) and play some roles in mRNA metabolism.
...
PMID:SUG1, a component of the 26 S proteasome, is an ATPase stimulated by specific RNAs. 928 26

In the framework of the EU programme for systematic sequencing of the Saccharomyces cervisiae genome we determined the sequence of a 9359 bp fragment of the right arm of chromosome VII. Five open reading frames (ORFs) of at least 300 nucleotides were found in this region. YGR267c encodes a protein with significant similarity to the enzyme GTP-cyclohydrolase I, that controls the first step in the biosynthetic pathway leading to various pterins and shows a high degree of sequence conservation from bacteria to mammals. We have recently demonstrated (Nardese et al., 1996) that YGR267c corresponds to the FOL2 gene, previously localized in the same chromosomal region by genetic mapping. The protein deduced from YGR270w belongs to the superfamily of putative ATPases associated with diverse cellular activities. It corresponds to the YTA7 gene, a member of a set of yeast genes coding for putative ATPases with high similarity to constituents of the 26S protease. The three ORFs YGR266w, YGR268c and YGR269w encode putative products of unknown function, with neither significant similarity to proteins in databases nor recognizable domains. YGR268c and YGR269w are partially overlapping ORFs: YGR268c seems to correspond to a real gene. whereas YGR269w is probably a fortuitous ORF.
...
PMID:A 9359 bp fragment from the right arm of Saccharomyces cerevisiae chromosome VII includes the FOL2 and YTA7 genes and three unknown open reading frames. 960 9

The hematopoietic proto-oncogene vav has been characterized as a Rac1-GDP/GTP exchanger protein which regulates cytoskeletal reorganization as well as signaling pathways leading to the activation of stress-activated protein kinases (SAPK/JNKs). Furthermore, vav overexpression enhances basal and T-cell receptor (TCR)-mediated stimulation of the nuclear factor of activated T cells (NFAT). We report here the interaction between Vav and hSiah2, a mammalian homolog of Drosophila Seven in absentia (Sina) that has been implicated in R7 photoreceptor cell formation during Drosophila eye development via the proteasome degradation pathway. Vav and hSiah2 interact in vitro and in vivo and colocalize in the cytoplasm of hematopoietic cells. The Src homology domain of Vav and the C-terminal region of hSiah2 are required for this interaction. We provide evidence for a negative regulation by hSiah2 of Vav-induced basal and TCR-mediated NFAT-dependent transcription. Overexpression of hSiah2 also inhibits the onco-Vav-induced JNK activation. Although the Vav-interacting domain is located in the C-terminal portion of hSiah2, the N-terminal region of hSiah2 is necessary for the inhibitory role that seems to be independent of the proteasome degradation.
...
PMID:hSiah2 is a new Vav binding protein which inhibits Vav-mediated signaling pathways. 1020 3

In eukaryotes, the 20 S proteasome is the proteolytic core of the 26 S proteasome, which degrades ubiquitinated proteins in an ATP-dependent process. Archaebacteria lack ubiquitin and 26 S proteasomes but do contain 20 S proteasomes. Many archaebacteria, such as Methanococcus jannaschii, also contain a gene (S4) that is highly homologous to the six ATPases in the 19 S (PA700) component of the eukaryotic 26 S proteasome. To test if this putative ATPase may regulate proteasome function, we expressed it in Escherichia coli and purified the 50-kDa product as a 650-kDa complex with ATPase activity. When mixed with the well characterized 20 S proteasomes from Thermoplasma acidophilum and ATP, this complex stimulated degradation of several unfolded proteins 8-25-fold. It also stimulated proteolysis by 20 S proteasomes from another archaebacterium and mammals. This effect required ATP hydrolysis since ADP and the nonhydrolyzable analog, 5'-adenylyl beta, gamma-imidophosphate, were ineffective. CTP and to a lesser extent GTP and UTP were also hydrolyzed and also stimulated proteolysis. We therefore named this complex PAN for proteasome-activating nucleotidase. However, PAN did not promote the degradation of small peptides, which, unlike proteins, should readily diffuse into the proteasome. This ATPase complex appears to have been the evolutionary precursor of the eukaryotic 19 S complex, before the coupling of proteasome function to ubiquitination.
...
PMID:An archaebacterial ATPase, homologous to ATPases in the eukaryotic 26 S proteasome, activates protein breakdown by 20 S proteasomes. 1047 46

The 20S proteasome is a self-compartmentalized protease which degrades unfolded polypeptides and has been purified from eucaryotes, gram-positive actinomycetes, and archaea. Energy-dependent complexes, such as the 19S cap of the eucaryal 26S proteasome, are assumed to be responsible for the recognition and/or unfolding of substrate proteins which are then translocated into the central chamber of the 20S proteasome and hydrolyzed to polypeptide products of 3 to 30 residues. All archaeal genomes which have been sequenced are predicted to encode proteins with up to approximately 50% identity to the six ATPase subunits of the 19S cap. In this study, one of these archaeal homologs which has been named PAN for proteasome-activating nucleotidase was characterized from the hyperthermophile Methanococcus jannaschii. In addition, the M. jannaschii 20S proteasome was purified as a 700-kDa complex by in vitro assembly of the alpha and beta subunits and has an unusually high rate of peptide and unfolded-polypeptide hydrolysis at 100 degrees C. The 550-kDa PAN complex was required for CTP- or ATP-dependent degradation of beta-casein by archaeal 20S proteasomes. A 500-kDa complex of PAN(Delta1-73), which has a deletion of residues 1 to 73 of the deduced protein and disrupts the predicted N-terminal coiled-coil, also facilitated this energy-dependent proteolysis. However, this deletion increased the types of nucleotides hydrolyzed to include not only ATP and CTP but also ITP, GTP, TTP, and UTP. The temperature optimum for nucleotide (ATP) hydrolysis was reduced from 80 degrees C for the full-length protein to 65 degrees C for PAN(Delta1-73). Both PAN protein complexes were stable in the absence of ATP and were inhibited by N-ethylmaleimide and p-chloromercuriphenyl-sulfonic acid. Kinetic analysis reveals that the PAN protein has a relatively high V(max) for ATP and CTP hydrolysis of 3.5 and 5.8 micromol of P(i) per min per mg of protein as well as a relatively low affinity for CTP and ATP with K(m) values of 307 and 497 microM compared to other proteins of the AAA family. Based on electron micrographs, PAN and PAN(Delta1-73) apparently associate with the ends of the 20S proteasome cylinder. These results suggest that the M. jannaschii as well as related archaeal 20S proteasomes require a nucleotidase complex such as PAN to mediate the energy-dependent hydrolysis of folded-substrate proteins and that the N-terminal 73 amino acid residues of PAN are not absolutely required for this reaction.
...
PMID:Biochemical and physical properties of the Methanococcus jannaschii 20S proteasome and PAN, a homolog of the ATPase (Rpt) subunits of the eucaryal 26S proteasome. 1069 74

Bidirectional transport of proteins via the Sec61p translocon across the endoplasmic reticulum (ER) membrane is a recognized component of the ER quality control machinery. Following translocation and engagement by the luminal quality control system, misfolded and unassembled proteins are exported from the ER lumen back to the cytosol for degradation by the proteasome. Additionally, other ER contents, including oligosaccharides, oligopeptides, and glycopeptides, are efficiently exported from mammalian and yeast systems, indicating that bidirectional transport across ER membranes is a general eukaryotic phenomenon. Glycopeptide and protein export from the ER in in vitro systems is both ATP- and cytosol-dependent. Using a well established system to study glycopeptide export and conventional liquid chromatography, we isolated a single polypeptide species of 23 kDa from rat liver cytosol that was capable of fully supporting glycopeptide export from rat microsomes in the presence of an ATP-regenerating system. The protein was identified by mass spectrometric sequence analysis as guanylate kinase (GK), a housekeeping enzyme critical in the regulation of cellular GTP levels. We confirmed the ability of GK to substitute for complete cytosol by reconstitution of glycopeptide export from rat liver microsomes using highly purified recombinant GK from Saccharomyces cerevisiae. Most significantly, we found that the GK (and hence the cytosolic component) requirement was fully bypassed by low micromolar concentrations of GDP or GTP. Similarly, export was inhibited by non-hydrolyzable analogues of GDP and GTP, indicating a requirement for GTP hydrolysis. Membrane integrity was fully maintained under assay conditions, as no ER luminal proteins were released. Competence for glycopeptide export was abolished by very mild protease treatment of microsomes, indicating the presence of an essential protein on the cytosolic face of the ER membrane. These data demonstrate that export of glycopeptide export is controlled by a microsomal GTPase and is independent of cytosolic protein factors.
...
PMID:A microsomal GTPase is required for glycopeptide export from the mammalian endoplasmic reticulum. 1091 37

Strict quality control mechanisms within the mammalian endoplasmic reticulum act to prevent misfolded and unprocessed proteins from entering post-endoplasmic reticulum (ER) compartments. Following translocation into the ER lumen via the Sec61p translocon, nascent polypeptide chains fold and are modified in an environment that contains numerous chaperones and other folding mediators. Recently it has emerged that polypeptides failing to acquire the native state are re-exported from the ER to the cytosol for ultimate degradation by the proteasome ubiquitin system, apparently mediated again via Sec61p. Substrates for this degradation pathway include proteins destined to become glycosyl phosphatidylinositol (GPI)-anchored, but which fail to be processed and retain the C-terminal GPI signal peptide. In order to characterise this process we have used a model GPI-anchored mutant protein, prepro mini human placental alkaline phosphatase (PLAP) W179, which cannot be processed efficiently on account of being a poor substrate for the transamidase which cleaves the GPI signal peptide and adds the GPI anchor in a coupled reaction. In vitro transcription, translation and translocation into canine pancreatic microsomes resulted in ER-targeting signal sequence cleavage and formation of prominiPLAP in the ER lumen. We were able to show that prominiPLAPW179 could be exported from the microsomes in a time-dependent manner and that release requires both ATP and cytosol. Export was not supported by GTP, indicating a biochemical distinction from glycopeptide export which we showed recently requires GTP hydrolysis. The process was not affected by redox, unlike several other GPI-anchored model proteins. These data demonstrate that misprocessed proteins can be exported in vitro from mammalian microsomes, facilitating identification of factors involved in this process.
...
PMID:Export of a misprocessed GPI-anchored protein from the endoplasmic reticulum in vitro in an ATP- and cytosol-dependent manner. 1103 51

Biogenesis of phagolysosomes proceeds through a sequential series of interactions with endocytic organelles, a process known to be regulated by Rab and SNARE proteins. The molecular mechanisms underlying phagosome maturation in neutrophils are, however, not clearly understood. We investigated fusion between phagosomes containing the intracellular pathogen Mycobacterium tuberculosis versus the extracellular pathogen Staphylococcus aureus (designated MCP for mycobacteria-containing phagosome and SCP for S. aureus-containing phagosome) and cytoplasmic compartments in human neutrophils. Western blot analysis of phagosomes isolated after internalisation revealed that lactoferrin (a constituent of secondary granules) and LAMP-1 were incorporated into both SCP and MCP, whereas hck (marker of azurophil granules) interacted solely with SCP. The subcellular distribution of the proteins Rab5a and syntaxin-4 suggested a role in docking of granules and/or endosomes to the target membrane in the neutrophil. We observed that during phagocytosis, Rab5a in GTP-bound form interacted with syntaxin-4 on the membrane of MCP and were retained for up to 90 minutes, whereas the complex was recruited to the SCP within 5 minutes but was selectively depleted from these vacuoles after 30 minutes of phagocytosis. Downregulation of Rab5a by antisense oligonucleotides efficiently reduced the synthesis of Rab5a, the binding of syntaxin-4 to MCP and SCP and the capacity for fusion exhibited by the pathogen-containing phagosomes, but it had no effect on bacteria internalisation. These data indicate that the difference in granule fusion is correlated with a difference in the association of Rab5a and syntaxin-4 with the phagosomes. Intracellular pathogen-containing phagosomes retain Rab5a and syntaxin-4, whereas extracellular pathogen-containing phagosomes bind briefly to this complex. These results also identified Rab5a as a key regulator of phagolysosome maturation in human neutrophils.
...
PMID:Rab5a GTPase regulates fusion between pathogen-containing phagosomes and cytoplasmic organelles in human neutrophils. 1188 31


<< Previous 1 2 3 4 5 6 7 8 Next >>

---