Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The site responsible for the mercaptan (or borohydride)-stimulated DNA scission activity of neocarzinostatin chromophore (NCS-Chrom) is located in the central C12-subunit of the molecule. This has been determined by studies of the characteristic spectral properties of the chromophore and its reduction products and of the spectral changes induced by their interaction with its apoprotein (apo-NCS) and DNA. The UV-visible absorption, fluorescence, CD, and MCD spectral properties of the major nonprotein chromophoric component of neocarzinostatin (NCS-Chrom A) are assigned to its component substructures, the 2-hydroxy-5-methoxy-7-methyl-1-naphthoate, the five-membered cyclic carbonate ring (1,3-dioxolan-2-one), the 2,6-dideoxy-2-methylaminogalactose, and the incompletely defined C12-subunit which links the other three residues. Although the major source of its UV-visible absorption is the naphthoic acid residue (HNA-NCS), a significant absorption from approximately 260 to 330 nm is due to the presence of the highly unsaturated C12-subunit. The presence of the C12-subunit and, to a lesser extent, the cyclic carbonate reduces the intensity of the fluorescence emission of the fluorophore of NCS-Chrom A, the HAN-NCS subunit. The CD activity of NCS-Chrom A is also due to the presence of the C12-subunit. The MCD activity of NCS-Chrom A, however, is completely accounted accounted for by the naphthoic acid residue. A role for the C12-subunit in the binding of NCS-Chrom to DNA or apo-NCS is indicated by the resultant absorption hypochromicity in the region assigned to the C12-moiety. Limited modification of the C12-subunit (by mercaptan or borohydride) inactivates the chromophore for DNA strand scission, although both products still bind DNA. The naphthoic acid residue alone is not sufficient for binding to DNA. Therefore, the intercalation of the naphthoate residue between DNA base pairs requires the binding of NCS-Chrom to DNA probably via electrostatic interaction between the positively charged 2-methylamino group of the galactose residue and the negatively charged oxygens of the phosphate in the DNA backbone. The C12-unit is viewed as forming a short-lived reduction-activated species that, in the presence of oxygen, causes single-strand breaks in DNA. The cyclic carbonate residue is not required for in vitro DNA strand scission activity but affects its stability with respect to hydrolysis and reactivity with mercaptan. If DNA is absent the activated species decompose to inactive products, including a mercaptan (or hydrogen) addition product of the C12-subunit.
Mol Pharmacol 1983 Mar
PMID:Neocarzinostatin chromophore. Assignment of spectral properties and structural requirements for binding to DNA. 622 Feb 5

The study of internal mobility in enzymes is of considerable importance for the understanding of their catalytic function, which cannot be adequately described as a property of a rigid protein. [13C]NMR spectroscopy permits simultaneous and selective observation of spectral lines from carbon atoms in many different residues in the enzyme with the chemical shift and relaxation parameters sensitive to structure, conformation and local motion. The changes in internal mobility in bovine carbonic anhydrase B (carbonate hydrolase, EC 4.2.1.1) in the native form and at various stages of denaturation are studied. Measurements of the relaxation parameters (T1, T1 rho) and of the NOE of 13C nuclei in the native protein showed that the extensive beta-sheet together with groups in the active center has a considerable internal librational mobility with tau G about 10(-11) s. This librational mobility is fairly uniform for all the alpha-carbons in the native enzyme. The use of a semiempirical modification of the motional theory proposed by Woessner allows to use simultaneously all the relaxation parameters measured in order to determine reliable values of the various correlation times.
Mol Biol (Mosk)
PMID:[Study of bovine carbonic anhydrase by 13C-NMR-spectroscopy]. 641 Jan 81

Chloride ions stimulated the ATP-dependent formation of a proton gradient in vesicles derived from amoebae of the cellular slime mould, D. discoideum, and reduced the formation of a membrane potential, inhibited rather than stimulated the formation of the proton gradient. Since bicarbonate ions did not inhibit H(+)-ATPase activity we conclude that they enter the vesicles and combine with translocated protons. This finding is consistent with the suggestion that the membranes of the light vesicle fraction are fragments of contractile vacuole complexes, and that these organelles increase their osmotic activity by taking up bicarbonate ions and protons from the cytoplasm, and then release water and carbonic acid into the extracellular milieu.
Biochem Mol Biol Int 1995 Aug
PMID:Anion effects on vesicle acidification in Dictyostelium. 758 Oct 1

The influence of two buffer systems (Hepes and CO2/HCO3-) on intracellular Ca2+ ([Ca2+]i) transients evoked by TRH and by elevated K+ were studied in single, and small clusters of, clonal rat pituitary GH4C1 cells using Fura 2. The steady-state level of [Ca2+]i was virtually identical in Hepes and CO2/HCO3-. In both buffers, addition of TRH induced a transient increase in [Ca2+]i which attained a significantly higher peak in Hepes (357 +/- 43 nM) when compared with values measured in the presence of CO2/HCO3- (184 +/- 21 nM). In Hepes, the basal IP3-level was higher than in CO2/HCO3-. The TRH-evoked increase in IP3 was higher in magnitude in Hepes than in CO2/HCO3-, although the stimulated/basal ratio was not different between the two buffers. The buffer composition had no effect on the specific binding of 3H-TRH to the cells. Furthermore, the amplitude of the increase in [Ca2+]i evoked by 50 mM K+ was identical in both buffers. TRH and K+ had no effect on pHi in either buffer. The present results indicate that HCO3- has an influence on TRH-induced Ca2+ transient, at least in part by modifying the TRH-evoked production of IP3.
Mol Cell Endocrinol 1995 Jul
PMID:Influence of Hepes- and CO2/HCO(3-)-buffer on Ca2+ transients induced by TRH and elevated K+ in rat pituitary GH4C1 cells. 758 88

The highly acidic soluble organic matrix (SM) isolated from shells of the Antarctic scallop, Adamussium colbecki, was shown to consist of 1.5% carbohydrate by weight and 12.8% phosphate by weight. Total SM is composed of approximately 31% Asx, 29% Ser, and 18% Gly. Separation of the SM using RP-HPLC yielded a minimum of six protein fractions labeled RP-1 through RP-6 in order of elution off the column. The first fraction, RP-1, was found to be an effective inhibitor of calcium carbonate crystal nucleation in vitro suggesting a role for this protein in the regulation of shell mineralization. A less acidic fraction, RP-3, showed less inhibitory activity and dephosphorylation of RP-1 resulted in almost complete loss of inhibitory activity. Automated Edman degradation was used to sequence peptides generated by chemical cleavage of RP-1. Mild acid hydrolysis yielded peptides with sequences of N-S-G-D-D-D-D-G-G-OH, N-S-G-G-(S,G)-G-OH, and N-S-G-R-G-OH. Cleavage with hydroxylamine yielded peptides of N-D-D-D-D-D-D-D-D-OH, N-L-Y-Y-OH, and N-A-V-G-E-S-D-OH. These data suggest biochemical similarities between this SM and other SM proteins isolated from both calcium carbonate and calcium phosphate biominerals, and presents evidence of a primary domain structure similar to that described for oyster SM and phosphophoryn isolated from rat dentin.
Comp Biochem Physiol B Biochem Mol Biol 1995 Jun
PMID:Characterization of organic matrix macromolecules from the shells of the Antarctic scallop, Adamussium colbecki. 759 87

Previous studies on beta-adrenergic agonist regulation of ion transport in distal airways yielded discordant results. The present study was performed to further investigate this process in isolated bronchiolar epithelial cells and resolve the discrepancies. Epithelial enriched in rabbit nonciliated bronchiolar epithelial (Clara) cells responded to isoproterenol with a biphasic increase in transepithelial short circuit current (Isc) and decrease in transepithelial resistance (Rt). The first phase of the Isc response consisted of a transient, 11 microA/cm2 increase in current that was inhibited by HCO3(-)-free bathing solutions, but was not inhibited by amiloride, bumetanide, or Cl(-)-free bathing solutions. The ED50 for isoproterenol stimulation of the initial peak was 81 pM. The second phase was a prolonged, 27 microA/cm2 elevation in Isc. Amiloride in the apical bath inhibited basal Isc and the prolonged change in Isc induced by isoproterenol. Bumetanide in the basolateral bath and bilateral Cl(-)-free bathing solutions likewise inhibited the plateau phase of the isoproterenol response, and the inhibition was accentuated in the presence of amiloride. HCO3(-)-free bathing solutions did not inhibit the plateau phase. The ED50 for isoproterenol stimulation of the plateau phase was 6.3 nM. The bioelectric response to isoproterenol was mimicked by isobutylmethylxanthine (IBMX) and, to a lesser degree, by dibutyryl-cAMP. Culturing the cells in medium containing cholera toxin completely inhibited the bioelectric response, yet the preparations continued to respond to isoproterenol with an increase in cAMP production. These results indicated that beta-adrenergic stimulation of Clara cells induced electrogenic transepithelial secretion of Cl- and HCO3- and resolved discrepancies between previous studies.
Am J Respir Cell Mol Biol 1995 Sep
PMID:Beta-adrenergic regulation of Cl- and HCO3- secretion by Clara cells. 765 89

The Golgi complex consists of a series of stacked cisternae in most eukaryotes. Morphological studies indicate the existence of intercisternal cross-bridge structures that may mediate stacking, but their identity is unknown. We have identified a 400-kDa protein, giantin, that is localized to the Golgi complex because its staining in double immunofluorescence experiments was coincident with that of galactosyltransferase, both in untreated cells and in cells treated with agents that disrupt Golgi structure. A monoclonal antibody against giantin yielded Golgi staining in one avian and all mammalian cell types tested, indicating that giantin is a conserved protein. Giantin exhibited reduced mobility on nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was recovered in membrane fractions after differential centrifugation or sucrose flotation, and was not released from membranes by carbonate extraction. Thus, giantin appears to be an integral component of the Golgi membrane with a disulfide-linked lumenal domain. Strikingly, the majority of the polypeptide chain is cytoplasmically disposed, because large (up to 350 kDa) proteolytic fragments of giantin could be released from intact Golgi vesicles. This feature, a large contiguous cytoplasmic domain, is present in the calcium-release channel of muscle that cross-bridges the sarcoplasmic reticulum and transverse tubule membranes. Therefore, giantin's localization, conservation, and physical properties suggest that it may participate in forming the intercisternal cross-bridges of the Golgi complex.
Mol Biol Cell 1993 Jul
PMID:Giantin, a novel conserved Golgi membrane protein containing a cytoplasmic domain of at least 350 kDa. 769 Dec 76

Experiments were performed in cat papillary muscles in order to explore the possible existence of an electrogenic Na+/HCO3- cotransport. Developed tension (DT), intracellular pH (pHi) with the pH-sensitive dye 2'-7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) and resting membrane potential (Vm) with 3M KCl filled glass microelectrodes were measured. A change from HEPES to HCO3(-)-buffered superfusate induced an immediate decrease in pHi and DT followed by a recovery in which pHi and DT stabilized at values slightly higher than in HEPES buffer. Introduction of HCO3- hyperpolarized Vm by 8 +/- 2.3 mV (P < 0.05). SITS (0.1 mM) completely abolished the hyperpolarization and attenuated the recovery of both pHi and DT. Under steady-state conditions in HCO3- buffered media, SITS induced a depolarization compatible with the suppression of the entry of negative charges. Depolarization by high Ko+ (45 mM) elicited a rise in pHi of 0.07 +/- 0.02 (P < 0.05), that was reversed by returning Ko+ to normal. The depolarization-induced rise in pHi proved to be Na(+)-dependent, SITS sensitive and still occurred after EIPA (microM) blockade. All the evidence strongly supports the existence of an electrogenic Na+/HCO3- cotransport mechanism that participates in the regulation of myocardial pHi. At pHi of 6.94 this mechanism seems to contribute almost equally to the Na+/H+ exchanger to pHi regulation. However, acid equivalent extrusion is potentiated when both the Na+/H+ exchanger and the HCO3-dependent mechanism are simultaneously regulating pHi.
J Mol Cell Cardiol 1995 Jan
PMID:An electrogenic sodium-bicarbonate cotransport in the regulation of myocardial intracellular pH. 776 Mar 47

In the present study the hypothesis was tested that N-bromoacetyl-3,3',5-[125I]triiodothyronine (BrAc[125I]T3) is a useful affinity label for both type I and type III iodothyronine deiodinases (ID-I and ID-III). Therefore, the microsomal fractions of various rat tissues were tested for ID-I and ID-III activities, and microsomal proteins were labeled with BrAc[125I]T3 and analyzed by SDS-PAGE. In agreement with previous observations, high ID-I activities were found in liver, kidney and thyroid, and high ID-III activities in brain, in particular fetal brain, and placenta. SDS-PAGE of BrAc[125I]T3-labeled microsomes showed a prominent radioactive approximately 27 kDa protein (p27) in liver, kidney and thyroid, which was previously identified as ID-I, and a approximately 32 kDa protein (p32) in brain, in particular fetal brain, and placenta. A good correlation was found between the affinity labeling of p32 and the inactivation of ID-III by BrAcT3, suggesting that p32 represents ID-III or a subunit thereof. After treatment of microsomes with 0.05% deoxycholate or carbonate buffer (pH 11.5) p32 was still labeled by BrAc[125I]T3, indicating that p32 is a transmembrane protein. Although 3,3',5'-triiodothyronine (rT3) is not a substrate for ID-III, p32 was readily labeled with BrAc[125I]rT3. Labeling of p32 in rat brain microsomes by BrAc[125I]rT3 was not affected by addition of 100 microM unlabeled thyroxine (T4) or T3, whereas deiodination of [125I]T3 by ID-III was inhibited by 91 and 96% in the presence of 1 microM T4 and T3, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1995 Feb
PMID:Investigation of type I and type III iodothyronine deiodinases in rat tissues using N-bromoacetyl-iodothyronine affinity labels. 776 29

The anaerobic, parasitic protist, Trichomonas vaginalis, is characterized by the absence of mitochondria and the presence of double membrane bound organelles called hydrogenosomes. Succinyl-coenzyme A synthetase is a hydrogenosomal enzyme which catalyzes the formation of ATP via substrate-level phosphorylation. We have characterized genes encoding the alpha subunit of the hydrogenosomal protein succinyl-coenzyme A synthetase (SCS). The alpha-SCS of T. vaginalis is encoded by a multigene family composed of 3 similar genes that do not appear allelic. These 3 alpha-SCS genes encode a protein with a calculated molecular mass of approximately 32.5 kDa that has > 50% identity (> 70% similarity with alpha-SCSs from Escherichia coli, Thermus flavus, and rat liver mitochondria. Antibodies raised against recombinant T vaginalis alpha-SCS expressed in bacteria were used to isolate alpha-SCS proteins from purified hydrogenosomes. These proteins partition into the soluble fraction of hydrogenosomes treated with sodium carbonate at high pH, consistent with a matrix localization in the organelle. Amino-terminal sequencing of purified alpha-SCS proteins shows that mature proteins lack a short, leader sequence of 9 amino acids. These amino terminal sequences which are cleaved from T. vaginalis alpha-SCSs are similar to each other and to all other leader sequences identifed on hydrogenosomal proteins.
Mol Biochem Parasitol 1994 Aug
PMID:Molecular characterization of the alpha-subunit of Trichomonas vaginalis hydrogenosomal succinyl CoA synthetase. 780 80


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