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)

The rapid turnover of spermidine/spermine N1-acetyltransferase (SSAT), a key enzyme in the regulation of polyamine levels, was found to be mediated via ubiquitination and the proteasomal system. SSAT degradation was blocked by the binding of polyamines or of the polyamine analog, N1,N12-bis(ethyl)spermine (BE-3-4-3), to the protein, providing a mechanism for the increase of SSAT activity in response to these agents. Site-directed mutagenesis indicated that a number of residues including arginine 19, cysteine 122, histidine 126, glutamic acid 152, arginine 155, and methionine 167 were needed for protection of SSAT by BE-3-4-3. These residues have previously been shown to reduce the affinity for the binding of polyamines to the SSAT protein, and these results indicate that the change in protein configuration brought about by this binding renders the protein resistant to proteasomal degradation. Mutations to alanines of residues arginine 7, cysteine 14, and lysine 141 also prevented the protection by BE-3-4-3, and these residues may be required for the formation of the protected conformation. The rapid degradation of SSAT required the carboxyl-terminal region of the protein, and the two terminal glutamic acid residues at positions 170 and 171 were found to be of critical importance. Truncation of the protein to remove these residues or the mutation of either of these acidic residues to glutamine completely abolished the rapid degradation of SSAT. The addition of two extra lysine residues at the carboxyl terminus or the conversion of the glutamic acids at positions 170 and 171 to lysines also prevented SSAT degradation by the proteasome. These results show the key role of the acidic residues at the carboxyl terminus of the protein in reacting with the proteasome. In contrast, mutation of lysine 166 to alanine, which extends the length of the acidic region in the carboxyl-terminal fragment of SSAT, actually increased the rate of degradation of SSAT without affecting its stabilization by BE-3-4-3. The binding of BE-3-4-3 or polyamines is therefore likely to change the configuration of the SSAT protein in a way that prevents the exposure of the carboxyl-terminal region of the ubiquitinated protein to the proteasome.
...
PMID:Proteasomal degradation of spermidine/spermine N1-acetyltransferase requires the carboxyl-terminal glutamic acid residues. 911 88

Listeria monocytogenes is a facultative intracellular bacterial pathogen that spreads cell to cell without exposure to the extracellular environment. Bacterial cell-to-cell spread is mediated in part by two secreted bacterial phospholipases C (PLC), a broad spectrum PLC (PC-PLC) and a phosphatidylinositolspecific PLC (PI-PLC). PI-PLC is secreted in an active state, whereas PC-PLC is secreted as an inactive proenzyme (proPC-PLC) whose activation is mediated in vitro by an L. monocytogenes metalloprotease (Mpl). Analysis of PI-PLC, PC-PLC, and Mpl single and double mutants revealed that Mpl also plays a role in the spread of an infection, but suggested that proPC-PLC has an Mpl-independent activation pathway. Using biochemical and microscopic approaches, we describe three intracellular proteolytic pathways regulating PCPLC activity. Initially, proPC-PLC secreted in the cytosol of infected cells was rapidly degraded in a proteasome-dependent manner. Later during infection, PCPLC colocalized with bacteria in lysosome-associated membrane protein 1-positive vacuoles. Activation of proPC-PLC in vacuoles was mediated by Mpl and an Mpl-independent pathway, the latter being sensitive to inhibitors of cysteine proteases. Lastly, proPC-PLC activation by either pathway was sensitive to bafilomycin A1, a specific inhibitor of vacuolar ATPase, suggesting that activation was dependent on acidification of the vacuolar compartment. These results are consistent with a model in which proPC-PLC activation is compartment specific and controlled by a combination of bacterial and host factors.
...
PMID:Proteolytic pathways of activation and degradation of a bacterial phospholipase C during intracellular infection by Listeria monocytogenes. 918 69

The proteasome is a multicatalytic protease complex that plays a key role in diverse cellular functions. The peptide vinyl sulfone, carboxybenzyl-leucyl-leucyl-leucine vinyl sulfone (Z-L3VS) covalently inhibits the trypsin-like, chymotrypsin-like and, unlike lactacystin, also the peptidylglutamyl peptidase activity in isolated proteasomes, and blocks their function in living cells. Although described as a class of mechanism-based inhibitors for cysteine proteases, the peptide vinyl sulfone Z-L3VS and a 125I-labeled nitrophenol derivative (125I-NIP-L3VS) covalently modify the active site threonine of the catalytic beta subunits of the proteasome. Modification of Thermoplasma proteasomes demonstrates the requirement for a hydroxyl amino acid (threonine, serine) as nucleophile at the beta subunit's NH2 terminus. 125I-NIP-L3VS covalently modifies the HslV subunit of the Escherichia coli protease complex HslV/HslU, a reaction that requires ATP, and supports a catalytic mechanism shared with that of the eukaryotic proteasome.
...
PMID:Covalent modification of the active site threonine of proteasomal beta subunits and the Escherichia coli homolog HslV by a new class of inhibitors. 919 16

Recent studies have demonstrated that cell-permeant protease inhibitors arrest human fibroblasts in late G1. The target for the inhibitors has been claimed to be either the proteasome, or a calpain-like cysteine protease activity. In the present investigation, the progression of serum-stimulated WI-38 fibroblasts into S-phase was partially inhibited by the cell-permeant general inhibitor of cysteine proteases, E64d, but not by its non-permeant anolog, E64c. Exposure of fibroblasts in late G1 to the proteasome inhibitor, lactacystin, produced only a modest inhibition of progression into S-phase, and did not influence the extensive inhibition produced by the calpain-selective inhibitor, ZLLY-DMK. ZLLnV-CHO and ZLLL-CHO, which are reportedly selective for the proteasome, were less potent than ZLLY-DMK as inhibitors of S-phase progression. These results argue for the involvement of a calpain-like protease acting in late G1 to allow transit into S-phase.
...
PMID:Evidence for participation of a calpain-like cysteine protease in cell cycle progression through late G1 phase. 924 87

The role of NF-kappa B in regulating FasL-mediated cytotoxicity was investigated by using lactacystin. Lactacystin is a microbial metabolite known to inhibit only the protease activity of the proteasome, which is required for NF-kappa B translocation. When activated by immobilized anti-CD3 monoclonal antibody, hybridoma T cells (5D5) degraded I kappa B beta, translocated NF-kappa B into the nucleus, transcribed immediate-early genes and the Fas ligand (FasL) gene, and expressed FasL-mediated cytotoxicity. Lactacystin strongly blocked I kappa B beta degradation and the translocation of NF-kappa B (p50/RelA heterodimer), but had little effect on the expression of the transcription factors, Oct-1 and AP-1. Moreover, lactacystin did not inhibit the nuclear translocation of NF-ATp whereas cyclosporin A inhibited the translocation of both NF-kappa B and NF-ATp. The expression of c-myc and nur77, two immediate-early genes implicated in FasL gene activation, was blocked by lactacystin. Subsequently, the expression of FasL gene and FasL-mediated cytotoxicity was inhibited. LLnL, a well-known peptide aldehyde which inhibits the protease activities of the proteasome and cysteine proteases, also inhibited NF-kappa B translocation and FasL-mediated cytotoxicity. However, these events were not inhibited by the highly specific cysteine protease inhibitor E64. These observations provide further evidence that FasL cytotoxicity is regulated by the proteasome. Furthermore, lactacystin must be added early in order to efficiently inhibit the induction of FasL cytotoxicity, indicating that the early events are critical for FasL gene activation. Our study integrates the proteasome-dependent I kappa B degradation and NF-kappa B translocation into a T cell activation cascade which results in FasL gene activation and the expression of FasL-mediated cytotoxicity.
...
PMID:Proteasome regulation of Fas ligand cytotoxicity. 934 69

Small peptides, 8-10 amino acids long, derived from degradation of cytoplasmic proteins by a proteasome-proteinase complex, are usually presented and recognized by CD8+ cytolytic T lymphocytes (CTLs) associated with major histocompatibility complex (MHC) class I molecules. Recently synthetic peptides were used for the in vitro induction of tumor-specific CTLs, offering another strategy in the study of the immune-response repertoire and providing a new tool in cancer vaccination and immunotherapy. Peptides derived from otherwise normal proteins, overexpressed in many tumors as products of the protooncogene, may represent a target for an immune response. This is the case of HER-2/neu gene (also known as ErbB-2), encoding a cysteine-rich glycoprotein transmembrane receptor with tyrosine kinase activity (gp185neu). Recent data, demonstrating that HLA-A2.1-related peptides are able to stimulate in vitro CD8+ lymphocytes, Prompted us to study the binding to HLA-A2.1 molecules of several gp185 synthetic peptides containing a cystein residue and to define the relevance of this amino acid residue in the reduced or oxidated form of the sulfhydryl group. We found that monomers and their homodimers, linked by a disulfide bridge, bind to HLA-A2.1 molecules with overlapping affinity. These results suggest that additional amino acids of the nonapeptide do not prevent the binding and the HLA refolding through chemical or sterical interactions. This might be of particular relevance for the in vivo processing of cysteine-rich proteins. Because ErbB-2 molecules, as tumor-differentiation antigens in melanoma, are cysteine-rich molecules, it may be relevant to evaluate the possible role of the cystine residues interacting with the T-cell receptor. The recognition of these heterodimers by CD8+ lymphocytes will require functional in vivo studies.
...
PMID:MHC-peptide binding: dimers of cysteine-containing nonapeptides bind with high affinity to HLA-A2.1 class I molecules. 940 48

The tumor suppressor p53 is degraded by the ubiquitin-proteasome system. p53 was polyubiquitinated in the presence of E1, UbcH5 as E2 and MDM2 oncoprotein. A ubiquitin molecule bound MDM2 through sulfhydroxy bond which is characteristic of ubiquitin ligase (E3)-ubiquitin binding. The cysteine residue in the carboxyl terminus of MDM2 was essential for the activity. These data suggest that the MDM2 protein, which is induced by p53, functions as a ubiquitin ligase, E3, in human papillomavirus-uninfected cells which do not have E6 protein.
...
PMID:Oncoprotein MDM2 is a ubiquitin ligase E3 for tumor suppressor p53. 945 May 43

Subtilisin-like serine protease, which is associated with the dormant spores of Bacillus cereus, was solubilized by washing the spores with 2 M KCl and purified to homogeneity by carbobenzoxy-D-phenylalanine-liganded affinity column chromatography and hydrophobic interaction column chromatography. Enzyme activity was completely inhibited by reagents for sulfhydryl groups such as HgCl2 as well as by conventional subtilisin inhibitors, suggesting the enzyme to be cysteine-dependent. The enzyme retained activity in 5 M urea at 4 degrees C for at least 2 months, and the specific activity was 50 times that of subtilisin BPN when measured for a common chromogenic substrate, carbobenzoxy-glycyl-glycyl-L-leucine p-nitroanilide. The gene encoding this protease was cloned in Escherichia coli, and its nucleotide sequence was analyzed. The deduced amino acid sequence suggested that the protease is produced as a precursor comprising three portions; a signal sequence (28 amino acid residues), a prosequence (80 amino acid residues) and a mature enzyme (289 amino acid residues). The mature region of the enzyme had high similarity with a thermitase from Thermoactinomyces vulgaris (72% identity) and a thermostable alkaline protease from Thermoactinomyces sp. E79 (66% identity), which have the N-terminal sequence showing scarcely noticeable similarity with corresponding stretches of subtilisins and mercuric ion-sensitive free cysteine in the equivalent position of the primary structure.
...
PMID:A cysteine-dependent serine protease associated with the dormant spores of Bacillus cereus: purification of the protein and cloning of the corresponding gene. 953 82

The Gal6 protease is in a class of cysteine peptidases identified by their ability to inactivate the anti-cancer drug bleomycin. The protein forms a barrel structure with the active sites embedded in a channel as in the proteasome. In Gal6 the C termini lie in the active site clefts. We show that Gal6 acts as a carboxypeptidase on its C terminus to convert itself to an aminopeptidase and peptide ligase. The substrate specificity of the peptidase activity is determined by the position of the C terminus of Gal6 rather than the sequence of the substrate. We propose a model to explain these diverse activities and Gal6's singular ability to inactivate bleomycin.
...
PMID:The unusual active site of Gal6/bleomycin hydrolase can act as a carboxypeptidase, aminopeptidase, and peptide ligase. 954 96

CTL recognize peptides derived from protein Ags bound to MHC-class I molecules. Proteasomes probably participate in the generation of these peptide epitopes. We investigated the role of proteasomes in the presentation of endogenously synthesized short viral proteins. To this end, we employed proteasome and cysteine protease inhibitors and two closely related recombinant vaccinia viruses that code for 17- and 19-amino acid-long products encompassing murine CMV 9pp89 epitope. Presentation of both minigene products required processing to shorter peptides and was independent of ubiquitination. Proteasomes were necessary for processing the 17-mer product, and cysteine proteases were not required. In contrast, the 19-mer product could be processed in parallel either by proteasomes or by cysteine proteases independently. These results highlight the diversity of alternative processing pathways even for short peptidic Ags, provide evidence for the involvement of cysteine proteases in MHC class I presentation, and show that cleavage by cysteine proteases is governed by sequences flanking the epitope.
...
PMID:Selective involvement of proteasomes and cysteine proteases in MHC class I antigen presentation. 955 Mar 70


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---