Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Iodoacetamide (IAA) and its fluorescent derivative, 5-(2-iodoacetamidoethyl) amino-naphthalene-1-sulfonate (IAEDANS) specifically bind to a site on the C-terminal half of sarcoplasmic reticulum (SR) Ca2+,Mg2+-ATPase. The location of this specific binding site was identified. SR membranes were treated with 150 microM [14C]IAA at pH 7.0 and 30 degrees C. One mole of IAA per mole of ATPase was bound in 6 h without affecting the Ca2+-transport activity. [14C]IAA-labeled SR membranes were cleaved with BrCN, and 14C-labeled peptide fragments were separated by Sephadex LH-60 chromatography and then digested further with trypsin. A radioactive peptide (Ala-Cys 674-Cys-Phe-Ala-Arg) was purified by Sephadex LH-20 chromatography and C18 reversed phase HPLC (Cys denotes the [14C]IAA-binding site). IAEDANS-labeling was carried out by reacting SR membranes with 50 microM IAEDANS for 5 h, at pH 7.0 and 30 degrees C. A fluorescent peptide was successfully purified by the same procedures as for the IAA-labeled peptide, and the amino acid sequence analysis of this peptide revealed that the IAEDANS labeling site was identical with the IAA binding site.
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PMID:Reactive sulfhydryl groups of sarcoplasmic reticulum ATPase. II. Site of labeling with iodoacetamide and its fluorescent derivative. 295 12

The artificial insertion of increasing amounts of unsaturated fatty acids into human erythrocyte membranes modulated ATPase activities in a biphasic manner, depending on the number and position of double bonds, their configuration, and the chain length. Uncharged long-chain fatty acid derivatives with double bonds and short-chain fatty acids were ineffective. Stearic acid stimulated Na+ K+-ATPase only. Anionic and non-ionic detergents and alpha-lysophosphatidylcholine failed to stimulate ATPase activities at low, and inhibited them at high concentrations. Mg2+-AtPase activity was maximally enhanced by a factor of 2 in the presence of monoenoic fatty acids; half-maximal stimulation was achieved at a molar ratio of cis(trans)-configurated C18 acids/membrane phospholipid of 0.16 (0.26). Na+K+-ATPase activity was maximally augmented by 20% in the presence of monoenoic C18 fatty acids at 37 degrees C. Half-maximal effects were attained at a molar ratio oleic (elaidic) acid/phospholipid of 0.032 (0.075). Concentrations of free fatty acids which inhibited ATPases activities at 37 degrees C were most stimulatory at reduced temperatures. At 10 degrees C, oleic acid increased Na+K+-ATPase activity fivefold (molar ratio 0.22). Unsaturated fatty acids simulated the effects of calmodulin on Ca2+-ATPase of native erythrocyte membranes (i.e., increase of Vmax from 1.6 to 5 mumol PO43- . phospholipid-1 . hr-1, decrease of K'Ca from 6 microM to 1.4-1.8 microM). Stearic acid decreased K'Ca (2 microM) only, probably due to an increase of negative surface charges. A stimulation of Mg2+-ATPase, Na+K+-ATPase, and Ca2+-ATPase could be achieved by incubation of the membranes with phospholipase A2. An electrostatic segregation of free fatty acids by ATPases with ensuing alterations of surface charge densities and disordering of the hydrophobic environment of the enzymes provides an explanation of the results.
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PMID:Modulation of ATPase activities of human erythrocyte membranes by free fatty acids or phospholipase A2. 612 96