Increase in dissociation rate constants of cardiotonic steroid-brain (Na+ + K+)-ATPase complexes by reduction of the unsaturated lactone. (1/2)
Several cardiotonic steroids have been modified by reduction of the unsaturated lactone and their interactions with the sodium- and potassium-activated ATPase ((Na+ + K+)-ATPase) have been investigated. Reduction of the unsaturated lactone results in a decrease in binding affinity due primarily to an increase in the dissociation rate constant concomitant with a decrease in the activation free energy of dissociation. This decrease in activation free energy is about 2 to 4 kcal, which is approximately equal to the energy of one hydrogen bond. It is suggested that the increase in dissociation rate due to reduction of the unsaturated lactone may make possible the use of these compounds as affinity ligands for purification of the (Na+ + K+)-ATPase or an ouabain-binding fragment. (+info)Photoaffinity labeling of (Na+K+)-ATPase with [125I]iodoazidocymarin. (2/2)
A radioiodinated, photoactive cardiac glycoside derivative, 4'-(3-iodo-4-azidobenzene sulfonyl)cymarin (IAC) was synthesized and used to label (Na+K+)-ATPase in crude membrane fractions. In the dark, IAC inhibited the activity of (Na+K+)-ATPase in electroplax microsomes from Electrophorus electricus with the same I50 as cymarin. [125I]IAC binding, in the presence of Mg2+ and Pi, was specific, of high affinity (KD = 0.4 microM), and reversible (k-1 = 0.11 min-1) at 30 degrees C. At 0 degree C, the complex was stable for at least 3 h, thus permitting washing before photolysis. Analysis of [125]IAC photolabeled electroplax microsomes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (7-14%) showed that most of the incorporated radioactivity was associated with the alpha (Mr = 98,000) and beta (Mr = 44,000) subunits of the (Na+K+)-ATPase (ratio of alpha to beta labeling = 2.5). A higher molecular weight peptide (100,000), similar in molecular weight to the brain alpha(+) subunit, and two lower molecular weight peptides (12,000-15,000), which may be proteolipid, were also labeled. Two-dimensional gel electrophoresis (isoelectric focusing then SDS-PAGE, 10%) resolved the beta subunit into 12 labeled peptides ranging in pI from 4.3 to 5.5. When (Na+K+)-ATPase in synaptosomes from monkey brain cortex was photolabeled and analyzed by SDS-PAGE (7-14%), specific labeling of the alpha(+), alpha, and beta subunits could be detected (ratio of alpha(+) plus alpha to beta labeling = 35). The results show that [125I]IAC is a sensitive probe of the cardiac glycoside binding site of (Na+K+)-ATPase and can be used to detect the presence of the alpha(+) subunit in crude membrane fractions from various sources. (+info)Cymarine is a steroidal alkaloid compound, specifically a spirosolane type, that is found in certain plants such as Solanum americanum (American black nightshade) and S. seaforthianum (Seaforth's-side-fruit), although its pharmacological or biological significance remains unclear.
I'm sorry for any confusion, but "Cymarine" is not a recognized term in medical or scientific literature. It may be possible that you have misspelled or are thinking of a different term. If you have more information about where you encountered this term or its intended meaning, I would be happy to try and help further.
Cymarin - Wikipedia
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MeSH Browser
use CYMARINE to search TSIMARIN 1975-92. History Note. 91(75); was see under STROPHANTHINS 1975-90; TSIMARIN was see CYMARINE ... Cymarine Preferred Term Term UI T010218. Date01/01/1999. LexicalTag NON. ThesaurusID ... Cymarine Preferred Concept UI. M0005498. Registry Number. UK3LS8435E. Related Numbers. 508-77-0. Scope Note. A cardiotonic ... Cymarine. Tree Number(s). D04.210.500.155.580.130.750.250. D09.408.180.810.250. Unique ID. D003529. RDF Unique Identifier. http ...
MeSH Browser
use CYMARINE to search TSIMARIN 1975-92. History Note. 91(75); was see under STROPHANTHINS 1975-90; TSIMARIN was see CYMARINE ... Cymarine Preferred Term Term UI T010218. Date01/01/1999. LexicalTag NON. ThesaurusID ... Cymarine Preferred Concept UI. M0005498. Registry Number. UK3LS8435E. Related Numbers. 508-77-0. Scope Note. A cardiotonic ... Cymarine. Tree Number(s). D04.210.500.155.580.130.750.250. D09.408.180.810.250. Unique ID. D003529. RDF Unique Identifier. http ...