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

Cytochrome c oxidase from the inner membrane of yeast mitochondria consists of seven nonidentical protein subunits, three being synthesized on mitochondrial ribosomes (molecular weights I: 43 K, II: 34 K, and III: 24 K) and four being made on cytoplasmic ribosomes (molecular weights IV: 14 K, V: 12 K, VI: 12 K, and VII: 4.5 K). In the present study all four cytoplasmically synthesized subunits of the enzyme were isolated on a large scale using ion exchange chromatography and gel filtration. Their amino acid composition as well as their amino- and carbosy-terminal amino acid residues have been determined. Sequence determinations of subunits IV and VI are already in an advanced state. The sequence of subunit VI is characterized by a large amino-terminal stretch dominated by charged amino acid residues followed by a cluster of hydrophobic amino acids. The binding site of yeast cytochrome oxidase for cytochrome c was studied by chemical crosslinking experiments. The formation of a disulfide bridge between the two proteins was observed by using cytochrome c from yeast modified with 5-thionitrobenzoate at the cysteinyl residue in position 107. Alternatively, a disulfide between yeast cytochrome c and the oxidase could be formed directly by oxidation with copper phenanthroline. Gel electrophoresis of the crosslinked complexes in sodium dodecyl sulfate revealed a new protein band with an apparent molecular weight of 38 K. This new band appears to be derived from cytochrome c and from subunit III of cytochrome oxidase.
Mol Cell Biochem 1977 Feb 04
PMID:Structure of cytochrome c oxidase from baker's yeast - a progress report. Preparation of four subunits for amino acid sequence determination and attempts to localize the cytochrome c binding site. 19 98

In two fractions obtained from the bovine A. coronaria adenylate cyclase activity was identified and characterized. The adenylate cyclase activity of the 75,000 X g sediment shows a pH optimum at 7.4. The temperature dependence of this adenylate cyclase activity is linear when represented in the Arrhenius plot, and an Arrhenius activation energy of 13.2 kcal Mol-1 can be calculated for the enzyme reaction. The Km-value of the enzyme to ATP is 6 +/- 0.6 - 10(-4) M. The adenylate cyclase activity of the 75,000 X g sediment can be stimulated by NaF. 5'AMP and adenosine inhibit the adenylate cyclase activity of the 75,000 X g sediment. With regard to the enzyme activity, Mn++ and Co++ replace Mg++, but not Ca++. The monovalentcations Na+ and K+ do not influence the adenylate cyclase activity. In a particulate fraction containing plasma membranes, adenylate cyclase activity was also identified. This adenylate cyclase activity can be stimulated by catecholamines, noradrenaline, and isoproterenol. This stimulation can, however, only be proved for the enzyme in the coronaries of 9-week-old and 2-year-old animals. The adenylate cyclase activity from the coronaries of adult animals is not affected by catecholamines. These findings are discussed with regard to hypertension frequently found in adult animals.
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PMID:[Proof of adenylate cyclase activity in the coronary artery of cattle]. 19 28

Liver cells were prepared from rats fed a rachitogenic diet to investigate the hepatic metabolism of [alpha-1,2-3H2] vitamin D3. Rat hepatocytes suspended in Hanks medium rapidly took up labeled vitamin D3 from the incubation medium and converted this sterol to various metabolites, including 25-hydroxy vitamin D3 (25-OH-D3). There was steady increment in the cellular production of 25-OH-D3 and of the more polar metabolites of vitamin D3 over 3 hr of incubation as determined by thin layer chromatography. Neither the addition of cyclic nucleotides or dexamethasone to, nor the removal of calcium or phosphate from the medium resulted in changes in the rate of conversion of vitamin D3 to its products. Rats pretreated with sodium diphenylhydantoin converted labeled vitamin D3 to its metabolites at the same rate as control rats. These data indicate that isolated liver cells retain the capacity for vitamin D3 hydroxylation, but suggest that the rate of this process does not undergo rapid changes in response to metabolic stimulation.
Mol Cell Biochem 1977 May 03
PMID:In vitro metabolism of vitamin D3 by isolated liver cells. 19 79

Tritiated salmon calcitonin was prepared by methylation of the free amino groups using tritiated sodium borohydride as precursor. Specific radioactivity was measured in competitive inhibition studies with specific anticalcitonin antibodies or tubular membranes as binding sites for calcitonin. The value observed, approx. 4 Ci/mmol, corresponded to methylation of one third of the available N-H bonds. Tritiated calcitonin prepared in this way retained full biological activity as assessed in vitro by stimulation of adenylate cyclase and in vivo by rat bioassay. Tritiated calcitonin specifically bound to isolated renal cells and nonspecific binding did not exceed 10% of total binding. Equilibrium was obtained after 15 min incubation. The hormone-receptor complex could be dissociated in the presence of an excess of unlabelled calcitonin. This data shows that tritiated calcitonin can be used in metabolic and receptor studies.
Mol Cell Endocrinol 1977 Sep
PMID:Biological and immunological properties of tritiated salmon calcitonin. 20 May 9

Several characteristics of the binding of insulin and glucagon to human circulating mononuclear leukocytes have been studied. Functional analysis (latex bead ingestion) revealed that cell mixtures, as prepared according to Boyum and used generally in studies of insulin resistance in humans, consist of 20-29% phagocytic monocytes, with the remainder being lymphocytes. Partial separation of monocytes from lymphocytes on columns of Sephadex G-10, followed by correlation of insulin binding with cell type, confirms that the monocyte is the binding species. Insulin influenced neither glucose uptake nor the further conversion of glucose to lipids and CO2 by the leukocytes. The transport of alpha-aminoisobutyrate, a nonmetabolizable amino acid, into these cells was also unaffected by insulin. Monocyte/lymphocyte mixtures specifically bound glucagon and prostaglandin E1. At physiological concentrations of these hormones, steady states were reached in 15 min and 45 min, respectively. In contrast to the 8-10-fold increases in cellular cyclic AMP produced by prostaglandins, the effect of glucagon was very small but apparently real. Under appropriate preincubation conditions, sodium azide and iodoacetamide inhibited phagocytosis and insulin binding in parallel. The binding of glucagon was unaffected by these agents. Although both antimycin A and actinomycin D inhibited phagocytosis of the monocytes, only the former inhibited insulin binding; there was only a slight effect on glucagon binding. We would conclude that the binding of insulin to human circulating monocytes, although reflective of insulin resistance in diabetes mellitus and obesity, may not be to traditional receptors. In contrast, the binding of glucagon to lymphocyte/monocyte mixtures may be to function-linked receptors.
Mol Cell Endocrinol 1977 Oct
PMID:Hormone receptors: VI. On the nature of the binding of glucagon and insulin to human circulating mononuclear leukocytes. 20 May 11

Preparations of avian erythrocyte plasma membranes have been made which are in the form of sealed vesicles. Using these preparations the permeability of the membranes to N+, K+, Mg2+ and Ca2+ was measured. Monobutyryl cyclic AMP and cyclic AMP increased the permeability to Na+ and Ca+ under conditions where no protein phosphorylation could occur. The only effect of phosphorylation of membrane proteins was to reduce Ca+ permeability. It is thus concluded that cyclic AMP increases Na+ permeability in the avian erythroycte by a direct effect which does not involve protein phosphorylation.
Mol Cell Biochem 1978 Jun 28
PMID:Cyclic AMP increase the Na+ permeability of the avian erythrocyte membrane by a process which does not involve protein phosphorylation. 20 12

Preparations of human erythrocyte membranes have been made which are in the form of sealed vesicles and which behave as osmometers on suspension in solutions of simple inorganic salts. Using these preparations the permeability of the membranes to Na+, K+, Mg2+ and Ca2+ was measured. Cyclic AMP (but not cyclic GMP) increased the permeability of the membranes to Ca2+ with a half maximal effect at a concentration of 25 microgram but did not affect the permeability to the other ions tested. Phosphorylation of proteins in the erthrocyte membrane lowered the permeability to Ca2+ without affecting the permeability to the other ions tested and there was a good correlation between the time course of protein phosphorylation and decrease in Ca2+ permeability. It is postulated that the system through which cyclic AMP causes an initial rapid rise in Ca2+ permeability followed by increased phosphorylation of membrane proteins and reduced Ca2+ permeability may have a widespread occurrence in biological systems and serve to control the concentration of Ca2+ in the cytoplasm.
Mol Cell Biochem 1978 Jun 28
PMID:The effect of cyclic nucleotides and protein phosphorylation on the permeability of human erythrocyte ghosts to certain cations. 20 14

1. The mechanism underlying the raised leucocyte sodium content in fulminant hepatic failure was studied by measurement of sodium fluxes, (Na+ + K+)-dependent adenosine triphosphatase activity, and leucocyte ATP content. 2. The rate constant for sodium efflux in the leucocytes was significantly reduced, and attributable to reduced activity of the enzyme (Na+ + K+)-ATPase. Leucocyte ATP content was not significantly different from that of control cells. 3. Incubation of cells from patients in the sera of normal subjects resulted in a reversal of these changes. Inhibition of the leucocyte sodium efflux rate constants and (Na+ +K+)-ATPase of normal cells was achieved by incubation in sera from patients. 4. We suggest that the raised sodium content of leucocytes in fulminant hepatic failure is attributable to a defective sodium pumping mechanism, possibly due to a circulating toxin.
Clin Sci Mol Med 1978 Oct
PMID:A study in vitro of the sodium pump in fulminant hepatic failure. 21 31

1. The haemodynamic effects of oral converting enzyme inhibitor (SQ 14225) were assessed in eight patients with severe essential or renovascular hypertension. 2. Mean arterial pressure fell (149 +/- 5 to 127 +/- 8 mmHg, P less than 0.02), because of a fall in total peripheral resistance (6.9 +/- 0.53 to 5.7 +/- 0.40 kPa 1(-1)s m2) without a significant change in cardiac index. Two of the eight patients were non-responders without pressure reduction or a haemodynamic change. Sodium restriction (10 mmol/day) while the same dose of SQ 14225 was continued further lowered arterial pressure (137 +/- 8 to 111 +/- 12 mmHg, P less than 0.05) through further resistance reduction (6.5 +/- 0.53 to 5.2 +/- 0.40 kPa 1(-1)s m2, P less than 0.05). 3. Haemodynamic responses to head-up tilt (increased heart rate and resistance, decreased cardiac index) were unaffected by SQ 14225 regardless of sodium intake. 4. The pattern of reduction in peripheral resistance, with unchanged cardiac index, was similar to that produced by vasodilators acting at both arteriolar and venular levels.
Clin Sci Mol Med 1978 Nov
PMID:Haemodynamics of orally-active converting enzyme inhibitor (SQ 14225) in hypertensive patients. 21 68

Specific receptors for thyrotropin were found to exist in membranes from whole human subcutaneous fat tissue. The characteristics of the interaction of 125I-labelled thyrotropin with such receptors were determined and compared with the stable, high-affinity thyrotropin receptor shown previously to exist in guinea pig fat membranes. Specific binding was readily detectable using low concentrations of membranes (up to 80 microgram/ml), though specific binding was reduced at higher membrane concentrations. Increasing concentrations of unlabelled thyrotropin reduced fractional binding, revealing saturation of a population of mixed affinity sites (highest Ka of the order of 0.3 X 10(9) M-1). Little cross-reactivity was observed with other lipolytic or structurally related hormones, though some cross-reactivity was observed in the presence of human chorionic gonadotropin. Association was temperature-dependent and rapid at 37 degrees C, though prolonged incubation revealed some instability of binding at this temperature. Binding was reversible with a high dissociation rate constant, and was particularly sensitive to the presence of low concentrations of sodium or calcium ions. Using membranes prepared from isolated human fat cells, binding of thyrotropin was equally sensitive to the addition of cations.
Mol Cell Endocrinol 1978 Oct
PMID:Characterization of thyrotropin binding to specific receptors in human fat tissue. 21 61


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