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

In the yeast plasma-membrane H(+)-ATPase and other P-type ATPases, conformational changes are transmitted between cytoplasmic and membrane-embedded domains via a stalk region composed of cytoplasmic extensions of membrane segments 2, 3, 4, and 5. The present study has used a fluorescent maleimide (Alexa-488) to probe Cys residues introduced into stalk segments 4 and 5 of the yeast enzyme. In the case of S5, Cys substitutions along one face led to a constitutive, 5- to 10-fold activation of the ATPase in the absence of glucose. Based on homology with SERCA Ca(2+)-ATPase, this face is likely to be buried in the interior of the protein, close to the P domain. Three Cys residues on the opposite face of S5 (A668C, S672C, and D676C) were accessible to Alexa-488 under all conditions tested. In addition, three other Cys residues at or near the boundary between the two faces reacted with Alexa-488 only (V665C, L678C) or preferentially (Y689C) in plasma membranes from glucose-metabolizing cells; this result provides the first direct evidence for a change in conformation of S5 during glucose activation. For stalk segment 4, site-directed mutagenesis gave no sign of a role in glucose-dependent regulation. Rather, substitutions at 13 consecutive positions along S4 caused kinetic changes consistent with a shift in equilibrium from E2 to E1. Four Cys residues along this stretch of S4 (Q357C, K362C, S364C, and S368C) reacted with Alexa-488, indicating that they are exposed to the aqueous medium as predicted in the SERCA-based structural model.
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PMID:Use of a fluorescent maleimide to probe structure-function relationships in stalk segments 4 and 5 of the yeast plasma-membrane H+-ATPase. 1276 92

The Ca(2+)-ATPase of the sarcoplasmic reticulum (SERCA) of rabbit skeletal muscle was oxidized by Fe2+/H2O2/ascorbic acid (AA), a system which generates HO(.) radicals according to the Fenton reaction: (Fe2(+)+H2O2-->HO(.)+OH(-)+Fe(3+)) under conditions similar to the pathological state of inflammation. Under these conditions, when hydroxyl-radicals and/or ferryl-radicals are generated, a 50% decrease of the SERCA activity was observed, a significant decrease of SH groups and an increase of protein carbonyl groups and lipid peroxidation were identified. Two new bands, time dependent in density, appeared in the SERCA protein electrophoresis after incubation with the Fenton system (at approximately 50 and 75kDa), probably due to structural changes as supported also by trypsin digestion. Immunoblotting of DNPH derivatized protein bound carbonyls detected a time dependent increase after incubation of SERCA with the Fenton system. Trolox and the pyridoindole stobadine (50microM) protected SR against oxidation induced via the Fenton system by preventing SH group oxidation and lipid peroxidation. Pycnogenol((R)) and EGb761 (40microg/ml) protected SERCA in addition against protein bound carbonyl formation. In spite of the antioxidant effects, trolox and stobadine were not able to prevent a decrease in the SERCA Ca(2+)-ATPase activity. Pycnogenol and EGb761 even enhanced the decrease of the Ca(2+)-ATPase activity induced by the Fenton system, probably by secondary oxidative reactions.
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PMID:Protective effect of antioxidants against sarcoplasmic reticulum (SR) oxidation by Fenton reaction, however without prevention of Ca-pump activity. 1869 62