Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vivo, ubiquitin exists both free and conjugated through its carboxyl terminus to the alpha- and epsilon-amino groups of a wide variety of cellular proteins. Ubiquitin carboxyl-terminal hydrolytic activity is likely a necessary step in the regeneration of the ubiquitin cofactor from ubiquitin-protein conjugates. In addition, this type of activity is required to generate the active, monomeric ubiquitin from the only known gene products: the polyprotein precursor and various ubiquitin fusion proteins. Thus, this activity is of vital importance to systems that utilize ubiquitin as a cofactor. A generic substrate, ubiquitin ethyl ester, was previously developed [Wilkinson, K. D., Cox, M. J., Mayer, A. N., & Frey, T. (1986) Biochemistry 25, 6644-6649] and utilized here to monitor the fractionation of these activities from calf thymus. By use of a rapid HPLC assay, four distinct, ubiquitin-specific esterases were identified and separated. A previously undescribed activity has been resolved and characterized, in addition to the bovine homologue of ubiquitin carboxyl-terminal hydrolase purified from rabbit reticulocytes. Two other activities resemble deconjugating activities previously detected in crude extracts but not previously purified. These activities appear to form a family of mechanistically related hydrolases. All four activities are inhibited by iodoacetamide, indicating the presence of an essential thiol group, and are inhibited to various extents by manganese. All have specific ubiquitin binding sites as judged by the low observed Km values (0.6-30 microM). The carboxyl-terminal aldehyde of ubiquitin is a potent inhibitor of these enzyme activities, with Ki values approximately 1000-fold lower than the respective Km values.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Detection, resolution, and nomenclature of multiple ubiquitin carboxyl-terminal esterases from bovine calf thymus. 253 53

A new substrate for ubiquitin carboxyl-terminal hydrolase, the carboxyl-terminal ethyl ester of ubiquitin, has been synthesized by a trypsin-catalyzed transpeptidation. In the presence of 1.6 M glycylglycine ethyl ester, trypsin removes the carboxyl-terminal glycylglycine of ubiquitin and replaces it with the dipeptide ester. The equilibrium mixture under these conditions contains 30% ubiquitin ethyl ester and 70% hydrolysis product, the 74-residue fragment of ubiquitin. Ubiquitin ethyl ester can be purified by gel filtration and ion-exchange chromatography. The structure of this product has been verified by identification of the products of base hydrolysis, tryptic cleavage in aqueous solution, and peptide mapping. When ubiquitin ethyl ester is incubated with purified ubiquitin carboxyl-terminal hydrolase, specific cleavage of the ester linkage is observed. A rapid, sensitive assay is described utilizing high-performance liquid chromatography. By use of this assay, it has been shown that ubiquitin carboxyl-terminal hydrolase is inactivated in the absence of thiols. Optimal protective effects are seen with 10 mM dithiothreitol. The rate of catalysis is maximal at pH 8.5, with evidence for catalytically important groups with pK values of 5.2, 7.6, and 9.5. These findings are consistent with the participation of a thiol group in the active site. Native ubiquitin is a competitive inhibitor of ubiquitin ethyl ester hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Synthesis and characterization of ubiquitin ethyl ester, a new substrate for ubiquitin carboxyl-terminal hydrolase. 302 15

Ubiquitin is expressed in eukaryotic cells as precursors, fused via its carboxyl terminus either to other ubiquitin sequences in linear polyubiquitin arrays or to specific ribosomal proteins. In some of the polyubiquitin fusions a single amino acid (e.g., valine in humans) is attached to the carboxyl terminus. These gene products are rapidly (probably cotranslationally) cleaved by ubiquitin carboxyl-terminal hydrolase (UCH) enzymes; therefore, although ubiquitin precursors are suitable substrates for assays of UCH activity, they are difficult to isolate from nucleated cells. While the recombinant approach allows the production of ubiquitin precursors in prokaryotic cells (which do not contain the ubiquitin system), proteins produced in this manner require purification and may also be susceptible to modification by bacterial enzymes, e.g., adventitious proteolysis. As an alternative we have chemically synthesized human ubiquitin-valine. In the assay described here the cleavage of ubiquitin-valine to ubiquitin (77 and 76 residue proteins, respectively) by a purified recombinant Drosophila UCH was monitored by capillary electrophoresis. Mass spectrometry verified the precise cleavage of ubiquitin-valine, confirming that this synthetic protein is a UCH substrate. Synthetic ubiquitin-valine may serve as a generic substrate for UCHs allowing the purification and identification of new members of this enzyme family.
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PMID:Capillary electrophoresis assay for ubiquitin carboxyl-terminal hydrolases with chemically synthesized ubiquitin-valine as substrate. 917 92

Protein gene product 9.5 (PGP 9.5) is a neuron-specific protein which acts as a ubiquitin carboxyl-terminal hydrolase. It facilitates the conversion of polyubiquitin to monoubiquitin, which can be reused for another catalytic cycle. Monoubiquitin plays an important role in degrading abnormal and denatured proteins. Previously, we have reported that ubiquitin-like immunoreactivity is expressed in axonal swellings following compression trauma to the rat thoracic cord. It was characterized by fast occurrence, progressive increase and gradual disappearance over a period of 9 days. The expression of PGP 9.5 has now been studied in the same material. Control rats showed a weak PGP 9.5 immunoreactivity in the nerve cell bodies of the cord. Except for the corticospinal tracts, the axons of other longitudinal tracts were weakly stained. Accumulation of PGP 9.5 immunoreactivity occurred in expanded axons at the site of compression already 4 h after trauma. They became more frequent in number 1 and 4 days after injury and remained so over the entire observation period of 9 days. The labelled axons were randomly distributed in the longitudinal tracts, but were never found in the corticospinal tracts. The extent of immunoreactivity was related to the degree of impact on the cord. Compression injury thus induces accumulation of both ubiquitin and PGP 9.5 immunoreactivity in axonal expansions. The injured axons may have a mechanism for degradation of proteins by the ubiquitin-mediated proteolytic pathway and another mechanism for effective ubiquitin regenerative cycling by the action of PGP 9.5.
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PMID:Expression of the ubiquitin carboxyl-terminal hydrolase PGP 9.5 in axons following spinal cord compression trauma. An immunohistochemical study in the rat. 920 Dec 40

Ubiquitin carboxyl-terminal hydrolases (UCHs) are implicated in the proteolytic processing of polymeric ubiquitin. We have isolated a novel mouse gene for ubiquitin carboxyl-terminal hydrolase isozyme L4. The gene named Uchl4 encodes a novel member of the family of ubiquitin carboxyl-terminal hydrolases (UCHs) whose predicted amino acid sequence shows 95% identity to mouse UCH-L3 and 94% identity to human UCH-L3. Genomic structure, chromosome localization, and expression pattern of Uchl3 and Uchl4 were characterized in the mouse. Both Uchl3 and Uchl4 were expressed in various tissues examined; however, expression level was quite lower in Uchl4. While Uchl3 consists of at least 9 exons spanning about 12 kb, Uchl4 was an intronless gene with a size of about 2 kb. By PCR-based analysis with T31 radiation hybrid mapping panel, Uchl3 and Uchl4 were mapped on mouse chromosome 9 and 14, respectively.
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PMID:Cloning, expression, and mapping of a mouse gene, Uchl4, highly homologous to human and mouse Uchl3. 1134 70

This study describes and examines the structural and morphological properties of the hierarchically organized, aragonite cuttlebone forms for the common cuttlefish (Sepia officinalis, L.), including its main structural parts, the dorsal shield, and the chambers. Specifically, it complements the mechanism for the self-organized formation of aragonite, identifies the presence, and determines the role of soluble organic matrix (SOM) proteins in the morphogenesis of the cuttlebone's biomineral structures on the nanoscale. The structure and morphology of the cuttlebone were examined using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), and their thermal properties by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Proteins from the SOM were investigated using two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS), nano liquid chromatography tandem mass spectrometry (nano-LC ESI-MS) and Edman degradation. The results showed that the cuttlebone exhibited several diverse biomineral structures characterized by complex morphologies. Their formation is governed by the organic matrix, particularly proteins, which at the earliest stage of development provide templates for the initial extracellular nucleation of the aragonite nanocrystals. This is followed by a bottom-up morphogenesis, based on the nanoscale oriented aggregation and coalescence of primarily formed aragonite nanograins, which results in the hierarchically organized, nanostructured, aragonite forms. The molecular masses of the most pronounced SOM proteins from the dorsal shield were about 10, 15, 40 and 60kDa, while from the chambers they were 10, 20, 25, 30 and 45kDa. Peptide fragments corresponding to Sep7, Sep8, chitin synthase 1, ficoline-2, polyubiquitin and the ubiquitin carboxyl-terminal hydrolase 32-like protein were detected in the SOM, with these proteins having functional properties related to the biomineralization processes. In general, there are mostly acidic proteins present in alternatively glycosylated forms, which are common attributes of biomineralization-related proteins.
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PMID:Formation and morphogenesis of a cuttlebone's aragonite biomineral structures for the common cuttlefish (Sepia officinalis) on the nanoscale: Revisited. 2882 65