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)

In separated outer medullary collecting duct (MCD) cells, the time course of binding of the fluorescent stilbene anion exchange inhibitor, DBDS (4,4'-dibenzamido-2,2'-stilbene disulfonate), to the MCD cell analog of band 3, the red blood cell (rbc) anion exchange protein, can be measured by the stopped-flow method and the reaction time constant, tau TDBDS, can be used to report on the conformational state of the band 3 analog. In order to validate the method we have now shown that the ID50D,DBDS,MCD (0.5 +/- 0.1 microM) for the H2-DIDS (4,4'-diisothiocyano-2,2'-dihydrostilbene disulfonate) inhibition of tau DBDS is in agreement with the ID50,Cl-MCD (0.94 +/- 0.07 microM) for H2-DIDS inhibition of MCD cell Cl- flux, thus relating tau DBDS directly to anion exchange. The specific cardiac glycoside cation transport inhibitor, ouabain, not only modulates DBDS binding kinetics, but also increases the time constant for Cl- exchange by a factor of two, from tau Cl- = 0.30 +/- 0.02 sec to 0.56 +/- 0.06 sec (30 mM NaHCO3). The ID50,DBDS,MCD for the ouabain effect on DBDS binding kinetics is 0.003 +/- 0.001 microM, so that binding is about an order of magnitude tighter than that for inhibition of rbc K+ flux (KI,K+,rbc = 0.017 microM). These experiments indicate that the Na+,K+-ATPase, required to maintain cation gradients across the MCD cell membrane, is close enough to the band 3 analog that conformational information can be exchanged. Cytochalasin E (CE), which binds to the spectrin/actin complex in rbc and other cells. modulates DBDS binding kinetics with a physiological ID50,DBDS,MCD (0.076 +/- 0.005 microM); 2 microM CE also more than doubles the Cl- exchange time constant from 0.20 +/- 0.04 sec to 0.50 +/- 0.08 sec (30 mM NaHCO3). These experiments indicate that conformational information can also be exchanged between the MCD cell band 3 analog and the MCD cell cytoskeleton.
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PMID:Interactions between anion exchange and other membrane proteins in rabbit kidney medullary collecting duct cells. 259 38

Cytochalasins are cytoskeleton disrupters, and cytochalasin E has been reported to increase intestinal paracellular permeability. In this study, the cytochalasin E effect on galactose transport has been investigated. Ussing-type chamber experiments show an inhibitory effect of 20 microM cytochalasin E on unidirectional mucosal to serosal flux of galactose. On the contrary, the opposite unidirectional flux is not modified by the inhibitor. Results using intestinal everted sacs and rings confirm that galactose uptake by the tissue is diminished by cytochalasin E. The effect appears already after 5 min incubation, depends on cytochalasin E concentration, and does not occur in the absence of Na+. The inhibition is accompanied by an increase in the apparent K(m) of the active sugar transport (11.5 vs.15.8 mM) without significant change in the VmaX (10.6 vs. 9.1 micromol x g(-1) wet weight x 5 min(-1)). Cytochalasin E does not modify either galactose uptake by brush border membrane vesicles or Na(+)-K(+) ATPase activity in the enterocytes, indicating that the inhibitory effect on the Na(+)-dependent sugar transport cannot be explained as a direct effect on SGLT1 activity or as an indirect effect through the Na(+)-K(+) ATPase. Thus, our results suggest that cytochalasin E decreases SGLTI activity indirectly through cytoskeleton disruption.
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PMID:Galactose transport inhibition by cytochalasin E in rat intestine in vitro. 1053 99