Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To characterize the pharmacological properties of the slow calcium channel of human red blood cells, we studied the action of various calcium antagonists and two agonists on the 45Ca2+-influx. The Ca2+-ejecting ATPase was inhibited by vanadate. All dihydropyridine derivatives tested showed their inhibiting or stimulating effect on the channel at concentrations attainable in vivo (nitrendipine:Ki = 2.5; Bayer K 6244:Ki 5 microM; nicardipine:Ki = 15 microM, Ks = 0.5 microM; Ciba 28 392:Ki = 20, Ks = 0.3 microM; Ki = inhibition constant, Ks = stimulation constant). Of special interest was the biphasic behaviour (stimulation and inhibition) of the calcium antagonist nicardipine and the agonist Ciba 28 392. The maximum inhibition by the phenylalkylamine derivative verapamil was obtained at much higher concentrations (250 microM; Ki = 100). These data suggest that the calcium channel of human red blood cells has pharmacological properties very similar to the channel in heart and smooth muscle cells with respect to dihydropyridine action. Therefore, human red blood cells are an ideal model to study the action of calcium agonists and antagonists.
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PMID:Human red blood cells--an ideal model system for the action of calcium agonists and antagonists. 608 91

The positions, with respect to the plasma membrane, of lysine 905, contained in the peptide QRKIVE, and of lysine 1012, contained in the carboxy-terminal peptide, RPGGWVEKETYY, of ovine Na+/K(+)-transporting ATPase have been reported to be cytoplasmic and extracytoplasmic, respectively [Bayer, R. (1990) Biochemistry 29, 2551-2256]. These results from our laboratory have been reexamined using an extension of the same procedure. Sealed right-side-out vesicles were modified with pyridoxal phosphate and sodium [3H]borohydride in the presence and absence of saponin or cholate. The modified alpha polypeptide was isolated and digested with the proteinase from Staphylococcus aureus strain V8 or trypsin to produce one or the other of these two peptides. These digests were passed over immunoadsorbents, identical to those used by Bayer, directed against pyroglutamylRXIVE or -ETYY. Unlike in the earlier studies, however, in the present studies the modified, radioactive peptides bound and eluted from the immunoadsorbents were submitted to HPLC, and their respective mobilities were compared to those of the synthetic peptides that had also been modified with pyridoxal phosphate. In this manner, the correct, modified peptide could be positively identified, and its specific radioactivity could be estimated. When cholate was added to sealed vesicles, prior to modification, there was at least a 3-fold increase in the incorporation of radioactivity into lysine 1012, consistent with a cytoplasmic location for this residue.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The carboxy terminus of sodium and potassium ion transporting ATPase is located on the cytoplasmic surface of the membrane. 838 80

Regulatory phosphorylation of phospholamban and of SR Ca(2+)-ATPase SERCA2a isoform by endogenous CaM-K II in slow-twitch skeletal and cardiac sarcoplasmic reticulum (SR) is well documented, but much less is known of the exact functional role of CaM K II in fast-twitch muscle SR. Recently, it was shown that RNA splicing of brain-specific alpha CaM K II, gives rise to a truncated protein (alpha KAP), consisting mainly of the association domain, serving to anchor CaM K II to SR membrane in rat skeletal muscle [Bayer, K.-U., et al. (1998) EMBO J. 19, 5598-5605]. In the present study, we searched for the presence of alpha KAP in sucrose-density purified SR membrane fractions from representative fast-twitch and slow-twitch limb muscles, both of the rabbit and the rat, using immunoblot techniques and antibody directed against the association domain of alpha CaM K II. Putative alpha KAP was immunodetected as a 23-kDa electrophoretic component on SDS-PAGE of the isolated SR from fast-twitch but not from slow-twitch muscle, and was further identified as a specific substrate of endogenous CaM K II, in the rabbit. Immunodetected, (32)P-labeled, non-calmodulin binding protein, behaved as a single 23-kDa protein species under several electrophoretic conditions. The 23-kDa protein, with defined properties, was isolated as a complex with 60-kDa delta CaM K II isoform, by sucrose-density sedimentation analysis. Moreover, we show here that putative alphaKAP, in spite of its inability to bind CaM in ligand blot overlay, co-eluted with delta CaM K II from CaM-affinity columns. That raises the question of whether CaM K II-mediated phosphorylation of alpha KAP and triadin together might be involved in a molecular signaling pathway important for SR Ca(2+)-release in fast-twitch muscle SR.
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PMID:Phosphorylation of anchoring protein by calmodulin protein kinase associated to the sarcoplasmic reticulum of rabbit fast-twitch muscle. 1111 36