Identification and partial purification of a cytosolic activator of vacuolar H(+)-ATPases from mammalian kidney.
A factor that activates affinity-purified vacuolar H(+)-ATPase from bovine kidney microsomes was identified and partially purified from bovine kidney cytosol. The activator is a heat-stable, trypsin-sensitive acidic protein with a Mr by gel filtration of approximately 35,000. The activator increased the activity of renal microsomal and brush border H(+)-ATPase by over 60% but stimulated lysosomal H(+)-ATPase activity by only 28%; it had little or no activity against the remaining N-ethylmaleimide-insensitive ATPase in kidney microsomes and other transport ATPases. Stimulation of ATPase activity appeared to result from binding of the activator to the H(+)-ATPase. Activation was saturable, with a Hill coefficient of 1 at low protein concentrations. Both activator binding and stimulation of H(+)-ATPase activity were enhanced at pH values less than or equal to 6.5. The activator has selective effects on different H(+)-ATPases and is poised to activate the enzyme at low physiologic values of cytosolic pH; this newly identified cytosolic proteins may participate in the physiologic regulation of the vacuolar H(+)-ATPase.
Zhang
K
K
Department of Medicine and Cell Biology, Washington University School of Medicine, St. Louis, Missouri.
Wang
Z Q
ZQ
Gluck
S
S
D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D003600:Cytosol / Q000502:physiology; D004789:Enzyme Activation; D005033:Ethylmaleimide / Q000494:pharmacology; D007672:Kidney Cortex / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D008970:Molecular Weight; D011506:Proteins / Q000302:isolation & purification / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology*
D011506:Proteins; D006180:Proton-Translocating ATPases; D005033:Ethylmaleimide