Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of pH, temperature and guanidine hydrochloride concentration on the structure of ubiquitin, a polypeptide which can activate adenylate cyclase and can mimic thymopoietin induced differentiation of prothymocytes, were monitored using nuclear magnetic resonance spectroscopy. This relatively small polypeptide (molecular weight of 8541) exhibits a remarkable stability towards pH and temperature changes. At 7 M guanidine hydrochloride concentration, the structure of ubiquitin is essentially a random coil.
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PMID:Nuclear magnetic resonance studies of the denaturation of ubiquitin. 2 Jan 53

A chromatin protein, A24, a conjugate of histone H2A and evolutionally conserved ubiquitin, was virtually the only structural polypeptide that was present in interphase but missing in mitosis of a Chinese hamster cell line (DON). Because a 10% increase in the H2A/DNA ratio observed in interphase-mitosis transition explained the stoichiometric conversion of A24 to H2A, it appears that ubiquitin bound to H2A of nucleosomal surfaces in interphase is released at mitosis whereas the total H2A remains as a structural component of nucleosomes. Regardless of protein synthesis, ubiquitin was again bound to H2A when cells entered the G1 phase. Based on the electrostatic nature of the COOH-terminal region of H2A, where ubiquitin binds, and the mitosis-specific rise of covalently linked phosphates in histones H1 and H3, we propose that an ionic interaction between the positively charged H2A COOH-terminal regions on fibers and negatively charged phosphates linked to serine or threonine of H1 and H3 molecules on adjacent fibers could generate an assembly of chromatin fibers in mitosis.
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PMID:Disappearance of a structural chromatin protein A24 in mitosis: implications for molecular basis of chromatin condensation. 29 27

The molecule beta-lipotropin, composed of 91 amino acids (beta-LPH 1-91) has gained considerable importance in recent years. Its double role as the precursor of beta-MSH (beta-LPH 41-58) and beta-endorphin (beta-LPH 61-91) makes this peptide unique in its kind. Results are presented on the role of this molecule and on the complete characterization of two morphine-like peptides from human and sheep pituitaries. The structure-activity relationship of opiate activity is analyzed by scanning for this biological activity of many tryptic and CNBr fragments of beta-lipotropin. The unequivocal localization of one of the important synthesis sites of beta-endorphin in the pituitary neurointermediate lobe is presented. A peptide with partial sequence Met1, Leu8,15 and Lys6,11, 27, 29, 33 has been biosynthesized in large quantities and its ubiquitous nature and conservation of sequence speaks for its importance and possible presence in many living cells. This polypeptide was subsequently identified as ubiquitin, a non-histone fragment of the nuclear protein A-24.
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PMID:Beta-lipotropin precursor of beta-MSH and beta-endorphin. 38 58

The amino acid sequences of two polypeptide components of thymosin Fraction 5 termed thymosin alpha1 and polypeptide beta1 have been established. The sequences were determined by automatic Edman degradation of the intact molecules as well as by manual sequence analysis of the enzymatic cleavage products. Thymosin alpha1, an immunologically active polypeptide, is highly acidic with an isoelectric point of 4.2. This molecule is composed of 28 amino acid residues with acetylserine as the NH2 terminus. A chemically synthesized molecule of thymosin alpha1 has been found to be as active as the natural molecule in our bioassay systems. Polypeptide beta1 is a molecule consisting of 74 amino acid residues and has an isoelectric point of 6.7. This peptide is not biologically active in our assay systems, suggesting that it is not involved in thymic hormone action. The sequence of beta1 was found to be identical with ubiquitin and a portion of protein A24, a nuclear chromosomal protein. The relationships among these proteins are discussed.
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PMID:The chemistry and biology of thymosin. II. Amino acid sequence analysis of thymosin alpha1 and polypeptide beta1. 76 8

The complete amino acid sequence was determined for bovine ubiquitin, and adenylate cyclase stimulating polypeptide, which is probably represented universally in living cells. Ubiquitin has a molecular weight of 8451 and consists of a single polypeptide chain containing 74 amino acid residues. It contains four arginine residues but no cysteine or trytophan residues. The first 61 amino acid residues were obtained by automated Edman degradations. Tryptic digestion of maleated ubiquitin yielded four peptide fragments that were resolved by molecular sieve chromatography and coded in order of decreasing chain length (MT-1, MT-2, MT-3, and MT-4). The automated sequenator determinations on native ubiquintin provided overlapping sequence data for three of these fragments that gave an order of MT-1, MT-3, and then MT-2; Peptide MT-4, a dipeptide, was therefore assigned to the C terminus, and the placement of peptide MT-2 was corroborated by analysis of data from carboxypeptidase digestions of maleated ubiquitin. Peptide MT-2 was domaleated and sequenced by manual Edman degradations through a single lysine residue. It was cleaved at this residue with trypsin, and the two resultant peptides were separated by ion-exchange chromatography. Manual sequencing of the C-terminal demaleated tryptic peptide of MT-2 completed the sequence of MT-2 and that of native ubiquitin. The sequence of ubiquitin was further confirmed and supported by amino acid and parital sequence anlysis of fragments obtained by digestion of maleated ubiquitin with chymotrypsin or staphylococcal protease.
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PMID:The complete amino acid sequence of ubiquitin, an adenylate cyclase stimulating polypeptide probably universal in living cells. 117 Aug 80

Human monoamine oxidase A that had been synthesized in a reticulocyte lysate translation system was capable of binding to and inserting into either rat liver mitochondria or isolated mitochondrial outer membranes. The inserted form was as resistant to proteinase K as endogenous mitochondrial monoamine oxidase A. The insertion, but not the binding, of monoamine oxidase A was prevented by depleting the reaction mixture of either ATP (with apyrase) or ubiquitin (with purified antibodies against this polypeptide). Addition of ATP or ubiquitin, respectively, to these depleted mixtures restored the insertion of the enzyme. In the absence of mitochondria, in vitro synthesized monoamine oxidase A did not catalyze its own alkylation by the mechanism-based inhibitor, [3H]clorgyline. However, both monoamine oxidase A that had been membrane-inserted in vitro and monoamine oxidase A that had been bound to the mitochondria under conditions of ATP depletion catalyzed adduct formation. Furthermore, reaction of either clorgyline or another mechanism-based inhibitor, pargyline, with the membrane-bound enzyme during ATP depletion inhibited the insertion of monoamine oxidase A when ATP was restored. These observations indicate that monoamine oxidase A acquired a catalytically active conformation on interaction with the mitochondrial outer membranes prior to its ATP and ubiquitin-dependent insertion into the membrane.
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PMID:The insertion of monoamine oxidase A into the outer membrane of rat liver mitochondria. 130 56

One of the most predominantly ubiquitinated protein species in Chlamydomonas, of which the apparent molecular mass in SDS-PAGE was 28 kDa, was found to exist abundantly in nuclei. The 28-kDa ubiquitinated protein was purified to homogeneity from the isolated nuclei of Chlamydomonas, and its partial amino acid sequence was determined. The N-terminal peptide sequence was identical with that of ubiquitin. Sequences homologous to those Chlamydomonas ubiquitin [corrected] and wheat histone H2B, and paired sequences of both of them were found in arginylendopeptidase-digested or protease V8-digested polypeptide fragments of the 28-kDa ubiquitinated protein. Based on these results, it was concluded that Chlamydomonas 28-kDa ubiquitinated protein is monoubiquitinated histone H2B.
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PMID:Purification of Chlamydomonas 28-kDa ubiquitinated protein and its identification as ubiquitinated histone H2B. 131 4

Widespread neuritic dystrophy is a hallmark of Alzheimer's disease (AD) and, in a less severe form, of brain ageing in various mammalian species. By immunohistochemistry, diffuse dot-like staining for ubiquitin (Ubq), a polypeptide involved in the degradation of abnormal and short-lived proteins, has been associated with human brain ageing. The nature of the Ubq deposits was investigated by immunogold electron microscopy on autopsy samples from aged human and dog brains. Most of the dot-like staining was localized to the white matter and corresponded to myelinated dystrophic neurites filled by Ubq-labelled lysosomal dense bodies. They did not contain paired helical filaments or multilamellar bodies. A minority of Ubq deposits was represented by amorphous densities in focal enlargements of the myelin sheaths. Our findings show that the spectrum of Ubq changes in ageing brain is wider than formerly recognized, and support the hypothesis that a defective regulation of the lysosomal system might be involved in the pathogenesis of structural abnormalities both in the ageing brain and in Alzheimer's disease.
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PMID:Age-related ubiquitin deposits in dystrophic neurites: an immunoelectron microscopic study. 131 32

A large part of cellular proteins is in a dynamic state of turnover. Protein breakdown is responsible for essential cellular functions like modulation of key enzyme levels or removal of abnormal proteins. A major pathway for this selective proteolysis is mediated by the ubiquitin system, in which proteins are committed to degradation by their ligation to ubiquitin, a highly conserved 76 amino acid polypeptide. Recent evidence indicates that ubiquitination serves other functions besides marking proteins for destruction. As originally described for histones, the activities of several cellular proteins are reversibly regulated by ubiquitination and a successive de-ubiquitination step mediated by the activity of one or more isopeptidases.
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PMID:[Ubiquitin-dependent degradation and modification of proteins]. 131 16

The prevalence of pale bodies and Lewy bodies was studied in the substantia nigra of 12 patients with typical Parkinson's disease (PD), in 5 patients with diffuse Lewy body disease (DLBD), and in a group of neurologically normal controls. Anti-ubiquitin antibodies labelled pale bodies and Lewy bodies in typical PD and DLBD, and there was a strong positive correlation between numbers of ubiquitin-immunoreactive pale bodies and Lewy bodies. BF10, a monoclonal antibody against a phosphate-dependent epitope of neurofilament 155-kDa polypeptide subunit, immunolabelled 57% of Lewy bodies and 15% of pale bodies in typical PD. Some pale bodies and Lewy bodies were seen in the substantia nigra of 2 of 5 neurologically normal, aged controls, probably representing "incidental PD". We conclude that there is a close relationship between pale bodies and typical Lewy bodies in the substantia nigra in clinical varieties of PD, and that these inclusions share antigenic determinants. If pale bodies and Lewy bodies reflect separate aspects of the cellular pathology in PD, their formation probably occurs in parallel. Alternatively, these observations may suggest that pale bodies represent a stage in the formation of Lewy bodies.
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PMID:Relationships between Lewy bodies and pale bodies in Parkinson's disease. 132 Mar 23


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