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)

Thymidine kinase is an enzyme involved in DNA precursor metabolism and DNA replication. The synthesis of this enzyme is highly regulated during the cell cycle and the activity of the enzyme is also regulated by feedback inhibition. Genes encoding thymidine kinase have been extremely useful as selectable markers for introducing DNA into a number of cells. In order to study cell cycle regulation of thymidine kinase, the gene which encodes this enzyme, as well as aspects of DNA replication in the ciliated protozoan Tetrahymena thermophila, we have purified thymidine kinase from Tetrahymena. Two forms of thymidine kinase with native molecular masses of 59 kDa and 80 kDa have been identified and purified 6800- and 4600-fold, respectively. The 59-kDa enzyme, a homodimer of 30-kDa subunits, has been purified to near homogeneity and polyclonal antibodies have been raised against the 30-kDa subunit. Serological studies indicate that the two enzymes are antigenically distinct. The antibody against the Tetrahymena protein cross-reacts with a polypeptide in Chinese hamster ovary (CHO) cell extracts of 26 kDa which corresponds to the reported size of Chinese hamster thymidine kinase protein.
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PMID:Thymidine kinase from Tetrahymena thermophila. Purification and immunological analysis. 199 76

Type 1 hereditary tyrosinemia (HT) is an autosomal recessive disease characterized by a deficiency of the enzyme fumarylacetoacetate hydrolase (FAH; E.C.3.7.1.2). We have isolated human FAH cDNA clones by screening a liver cDNA expression library using specific antibodies and plaque hybridization with a rat FAH cDNA probe. A 1,477-bp cDNA was sequenced and shown to code for FAH by an in vitro transcription-translation assay and sequence homology with tryptic fragments of purified FAH. Transient expression of this FAH cDNA in transfected CV-1 mammalian cells resulted in the synthesis of an immunoreactive protein comigrating with purified human liver FAH on SDS-PAGE and having enzymatic activity as shown by the hydrolysis of the natural substrate fumarylacetoacetate. This indicates that the single polypeptide chain encoded by the FAH gene contains all the genetic information required for functional activity, suggesting that the dimer found in vivo is a homodimer. The human FAH cDNA was used as a probe to determine the gene's chromosomal localization using somatic cell hybrids and in situ hybridization. The human FAH gene maps to the long arm of chromosome 15 in the region q23-q25.
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PMID:Cloning and expression of the cDNA encoding human fumarylacetoacetate hydrolase, the enzyme deficient in hereditary tyrosinemia: assignment of the gene to chromosome 15. 199 38

Platelet-derived growth factor (PDGF), a key mitogen for liver fat-storing cells (FSC), is a dimeric molecule that occurs as homodimers or heterodimers of related polypeptide chains (PDGF-BB, -AB, and -AA). In chronic inflammation of the liver lobule, any of the three dimeric forms of PDGF derived from multiple sources could potentially interact with FSC. We explored the effects of the three different PDGF isoforms on DNA synthesis and early signal transduction pathways potentially related to PDGF mitogenicity in rat liver FSC. PDGF-BB homodimer and -AB heterodimer induced a marked increase in DNA synthesis, whereas the effect of PDGF-AA homodimer was considerably lower. Moreover, the mitogenicity of each isoform proportionally correlated with their effects on phosphoinositide turnover and intracellular Ca2+. Both the PDGF-BB and -AB dimers likely interact with the PDGF-beta-receptor, although PDGF-AB requires at least one alpha-receptor. The low responsiveness to PDGF-AA could not be accounted for by downregulation of the PDGF-alpha-receptor because FSC expressed very low levels of PDGF-A- and B-chain mRNAs and did not secrete detectable amounts of PDGF activity in the conditioned media. In addition, preincubation of FSC with suramin, a potent inhibitor of PDGF binding to its receptor, failed to increase PDGF-AA-induced DNA synthesis. These results are consistent with a predominant expression of PDGF-beta-receptor in liver FSC, that is linked to phospholipase C activation.
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PMID:Mitogenic signals for platelet-derived growth factor isoforms in liver fat-storing cells. 200 75

The nucleotide sequence of the gene cysH from Escherichia coli K12 was determined. The open reading frame was 735 nucleotides in length; it was flanked by a repetitive palindromic sequence centred 36 nucleotides upstream of cysH and a terminator-like structure located 20 nucleotides downstream. CysH encoded a polypeptide of Mr 27927 consisting of 244 amino acids. The gene product was isolated as a homodimer exhibiting phospho-adenylylsulphate reductase (PAPS reductase) activity. The active enzyme was devoid of electron transferring cofactors and contained only one cysteine per subunit. Reduction of the enzyme by dithiols resulted in a shift of the apparent molecular weight from 44,000 to 62,000 without formation of an enzyme-thioredoxin complex.
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PMID:Characterisation of the gene cysH and of its product phospho-adenylylsulphate reductase from Escherichia coli. 200 73

1. The redox properties of the active-site dithiol/disulphide groups of PDI were determined by equilibrating the enzyme with an excess of GSH + GSSG, rapidly alkylating the dithiol form of the enzyme to inactivate it irreversibly, and determining the proportion of the disulphide form by measuring the residual activity under standard conditions. 2. The extent of reduction varied with the applied redox potential; to a first approximation, the data fitted a model in which all the enzyme dithiol/disulphide groups are independent and equivalent and the equilibrium constant between these sites and the GSH/GSSG redox couple is 42 microM at pH 7.5. 3. The standard redox potential for PDI active-site dithiol/disulphide couples was calculated from this result and found to be -0.11 V; hence PDI is a stronger oxidant and weaker reductant than GSH, nicotinamide cofactors, thioredoxin and dithiothreitol. 4. The redox equilibrium data for PDI with the GSH/GSSG redox couple showed sigmoidal deviations from linearity. The sigmoidicity could be modelled closely by assuming a Hill coefficient of 1.5. 5. This evidence of co-operative interactions between the four active sites in a PDI dimer was extended by studying the reaction between PDI and homobifunctional alkylating agents with various lengths between the reactive groups. A species whose electrophoretic mobility suggested it contained an intrachain cross-link was observed in all cases, whereas there was no evidence for cross-linking between the chains of the PDI homodimer. Most effective cross-linking was achieved with reagents containing five or more methylene spacer groups, implying a minimum distance of 1.6 nm (16 A) between the active-site reactive groups within the two thioredoxin-like domains of the PDI polypeptide.
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PMID:Redox properties and cross-linking of the dithiol/disulphide active sites of mammalian protein disulphide-isomerase. 202 21

The proto-oncogene products Fos and Jun form a stable heterodimeric complex that functions in transcriptional regulation by interacting with the DNA sequence known as the AP-1 site. Dimer formation occurs through the leucine zipper, a structural motif involving a heptad repeat of leucine residues that is conserved in several fos- and jun-related genes. We have employed a novel cloning strategy to isolate genes encoding proteins capable of forming complexes with Jun. The procedure involves direct screening of a lambda gt11 cDNA library with a biotinylated Jun polypeptide. One clone isolated in this manner encodes CRE-BP1, a leucine zipper-containing protein that binds to the cyclic AMP response element (CRE) as a homodimer. CRE-BP1 also forms heterodimers with Jun but not with Fos. Jun binds cooperatively to the CRE in association with CRE-BP1. Thus, the DNA-binding specificity and affinity of Jun are modulated by association with Fos or with CRE-BP1.
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PMID:Direct cloning of leucine zipper proteins: Jun binds cooperatively to the CRE with CRE-BP1. 213 3

The human T lymphocyte Ag CD28 (Tp44) is a homodimeric glycoprotein expressed on the surface of a majority of human peripheral T cells and thymocytes. Although exposure of T cells to anti-CD28 mAb does not activate T cells, stimulation of CD28 can synergize with signals transmitted through the TCR or other stimuli to augment proliferation and lymphokine production. We have used a portion of the human CD28 cDNA to isolate a homologous murine cDNA from an EL4 T lymphoma library. The murine clone has 61% nucleotide identity with the human cDNA. Both human and murine sequences exhibit homology with members of the Ig supergene family and CTLA-4, a T cell specific murine gene. Many characteristics of the human CD28 molecule are conserved within the putative murine CD28 polypeptide. The murine cDNA sequence encodes a polypeptide of 218 amino acids that has 68% identity with the human sequence. Both the murine and human molecules are integral membrane glycoproteins with hydrophobic signal peptide sequences and transmembrane region. All five potential N-linked glycosylation sites are conserved and six of the seven cysteine residues of the mouse protein are found in the human CD28 polypeptide. The murine cDNA is encoded by a single copy nonrearranging gene whose expression at the mRNA level is restricted to T cells. A rabbit antiserum was raised against a synthetic peptide corresponding to a hydrophilic portion of the translated murine cDNA sequence. This antiserum identifies an 80-kDa homodimer consisting of disulfide-bonded subunits of 40 kDa that is expressed on splenic T cells, thymocytes, and several T cell tumors, but not on B cells. deglycosylation studies indicate that four of the five N-linked glycosylation sites are used and that the mature core protein has a molecular mass of 25 kDa, close to that predicted by the cDNA sequence. Transfection of the murine cDNA into Chinese hamster ovary cells resulted in the expression of an 80-kDa dimeric molecule that was immunoprecipitated by the antipeptide antiserum. Taken together, these data provide strong support that we have identified the murine homologue of CD28.
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PMID:The murine homologue of the T lymphocyte antigen CD28. Molecular cloning and cell surface expression. 215 64

This paper describes a large-scale purification procedure of the amiloride binding component of the epithelium Na+ channel. [3H]Phenamil was used as a labeled ligand to follow the purification. The first two steps are identical with those previously described [Barbry, P., Chassande, O., Vigne, P., Frelin, C., Ellory, C., Cragoe, E. J., Jr., & Lazdunski, M. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 4836-4840]. A third step was a hydroxyapatite column. The purified material consisted of a homodimer of two 88-kDa proteins that migrated anomalously in SDS-PAGE to give an apparent Mr of 105,000. Deglycosylation by treatment with neuraminidase and endoglycosidase F or with neuraminidase and glycopeptidase F indicated that less than 5% of the mass of the native receptor was carbohydrate. Sedimentation analysis of the purified Na+ channel in H2O and D2O sucrose gradients and gel filtration experiments led to an estimated molecular weight of the [3H]phenamil receptor protein-detergent-phospholipid complex of 288,000 and of the native [3H]phenamil receptor protein of 158,000. [3H]Br-benzamil is another labeled derivative of amiloride that recognized binding sites that had the same pharmacological properties as [3H]phenamil binding sites and that copurified with them. Upon irradiation of kidney membranes, [3H]Br-benzamil incorporated specifically into a 185-kDa polypeptide chain under nonreducing electrophoretic conditions and a 105-kDa protein under reducing conditions. The same labeling pattern was observed at the different steps of the purification. Reconstitution of the purified phenamil receptor into large unilamellar vesicles was carried out. A low but significant phenamil- and amiloride-sensitive electrogenic Na+ transport was observed.
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PMID:[3H]phenamil binding protein of the renal epithelium Na+ channel. Purification, affinity labeling, and functional reconstitution. 216 Feb 71

Antisera raised against two mitosis-specific protein kinases from human cells recognized a single 65-kDa polypeptide (p65) that is present in similar amounts in interphase and mitotic cell extracts. Immunoblot analysis of reduced and unreduced extracts revealed that p65 exists as a 65-kDa monomer during interphase but forms a 130-kDa disulfide-linked homodimer during mitosis. Several different antibodies recognizing the p34cdc2 protein kinase and cyclin B components of M phase-promoting factor (MPF) coprecipitated p65 from mitotic but not from interphase extracts. In addition, an anti-p65 immunoaffinity column substantially depleted mitotic extracts of histon H1 kinase activity assayed under conditions diagnostic for MPF. These results suggest that active human MPF may be a complex of p34cdc2, cyclin B, and dimeric p65. A sulfhydryl cycle, proposed in the earlier literature on the biochemistry of mitosis, might underlie the dimerization of p65 and formation of active MPF.
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PMID:Identification of mitosis-specific p65 dimer as a component of human M phase-promoting factor. 217 7

The complete amino acid sequence of the cyclic GMP stimulated cyclic nucleotide phosphodiesterase (cGS-PDE) of bovine heart has been determined by analysis of five digests of the protein; placement of the C-terminal 330 residues has been confirmed by interpretation of the corresponding partial cDNA clone. The holoenzyme is a homodimer of two identical N alpha-acetylated polypeptide chains of 921 residues, each with a calculated molecular weight of 103,244. The C-terminal region, residues 613-871, of the cGS-PDE comprises a catalytic domain that is conserved in all phosphodiesterase sequences except those of PDE 1 from Saccharomyces cerevisiae and a secreted PDE from Dictyostelium. A second conserved region, residues 209-567, is homologous to corresponding regions of the alpha and alpha' subunits of the photoreceptor phosphodiesterases. This conserved domain specifically binds cGMP and is involved in the allosteric regulation of the cGS-PDE. This regulatory domain contains two tandem, internal repeats, suggesting that it evolved from an ancestral gene duplication. Common cyclic nucleotide binding properties and a distant structural relationship provide evidence that the catalytic and regulatory domains within the cGS- and photoreceptor PDEs are also related by an ancient internal gene duplication.
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PMID:Amino acid sequence of the cyclic GMP stimulated cyclic nucleotide phosphodiesterase from bovine heart. 217 66


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