Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracellularly applied NADH, but not NAD or NADPH, increases the resting membrane potential from -74.1 to -76.6 mV in freshly isolated muscles in the presence of K+ in the incubation medium and from -64.6 to -72.9 mV in muscles equilibrated for 4-6 h in a K+-free solution. The NADH-induced hyperpolarization is blocked by pretreatment of muscles with ouabain, and the inhibitors of plasma membrane NADH dehydrogenase (adriamycin, azide, PCMB, atebrine, DIDS and bleomycin). The effect of NADH is accompanied by the disappearance of NADH from the incubation medium and by decreased membrane resistance. We conclude that NADH hyperpolarization is due to the enhancement of passive membrane permeability, apparently for K+, which might result from the conformational changes in the plasma membrane during the NADH dehydrogenase reaction. The possibility is discussed that NADH dehydrogenase mediates transport of K+ out from the cell using a pathway connected with the transmembrane Na+/K+ pump.
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PMID:Hyperpolarization of mouse skeletal muscle plasma membrane induced by extracellular NADH. 646 61

NADH dehydrogenase in the plasma membrane transfers electrons from NADH to external oxidants like ferricyanide, through pathways which are linked to metabolic processes in the cell. Hormone binding to specific sites (receptors) can modify the enzyme activity, suggesting a direct or indirect coupling between the redox system and the hormone receptors. Reduction of external ferricyanide to ferrocyanide by human erythrocytes was stimulated by beta-adrenergic agonists (adrenaline, ritodrine and isoxsuprine), this effect being dependent upon concentration and pH. The agonist-stimulatory effect was attenuated in the presence of metoprolol (10(-4) M), a beta-adrenergic antagonist, and was not modified in the presence of prazosin, an alpha-adrenergic antagonist, suggesting that modification of the redox activity is mediated by binding of the agonists to beta-adrenergic receptors present in the human erythrocytes. Basal and agonist-dependent activities were inhibited in the presence of sulfhydryl reagents p-chloromercuribenzoate (PCMB, 10(-5) M) and N-ethylmaleimide (NEM, 10(-3) M), indicating the involvement of -SH groups. Inactivation by NEM was reversed by washing the cells with GTP (10(-3) M) and GTP gamma S (10(-4) M), suggesting that the specific alkylated -SH group(s) is located on a G protein in the hormone-receptor-G-protein complex. The human erythrocytes contain G proteins, displaying both guanine-nucleotide-binding properties and GTPase activity. Fluoride (10(-2) M) and fluoroaluminate (AlF4- (F-, 10(-2) M + Al3+, 10(-5) M), G protein activators, enhanced the basal and agonist-dependent activities, suggesting the involvement of G proteins in this system. The overall results indicated that one of the coupling components between the hormonal receptors and the redox system is probably a G protein, and the mechanism of enzyme activation after hormone binding to the receptor is based on the redox state of cysteine residues probably within the receptor-G-protein complex.
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PMID:Activation of a NADH dehydrogenase in the human erythrocyte by beta-adrenergic agonists: possible involvement of a G protein in enzyme activation. 926 92