Inhibition of rat liver microsomal Ca2+-ATPase by fluorescein-5'-isothiocyanate.
Rat liver microsomal fraction was incubated at pH 8.8 with fluorescein-5'-isothiocyanate in a Tris-buffered sucrose medium. This treatment completely inhibited ATP-dependent Ca2+ transport, Ca2+-ATPase activity, and Ca2+-ATPase phosphoenzyme intermediate formation. Inhibition of Ca2+ transport and phosphoenzyme intermediate formation by fluorescein-5'-isothiocyanate was partially prevented by including ATP in the treatment medium. These data taken together are consistent with the proposal that fluorescein-5'-isothiocyanate binds the Ca2+-ATPase ATP-binding site, suggesting the presence of a lysine residue in this domain. Fluorescein-5'-isothiocyanate labeling of microsomal proteins had no measurable effect on the basal, Mg2+-ATPase activity. Using fluorescein-5'-isothiocyanate-labeled microsomal fraction, we demonstrated that the Mg2+-ATPase activity was inhibited by Ca2+.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins / Q000494:pharmacology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013861:Thiocyanates / Q000494:pharmacology*
D005452:Fluoresceins; D010750:Phosphoproteins; D013861:Thiocyanates; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D016650:Fluorescein-5-isothiocyanate; D002118:Calcium