MedicGo
Characterization studies on the membrane-bound adenosine triphosphatase (ATPase) of Azotobacter vinelandii.
Metadata
Journalcanadian journal of microbiology1.793Date
1975-Nov
Publication Type
Research Support, U.S. Gov't, P.H.S.
Journal Article
Volume
1975-Nov / 21 : 1807-14
Author
Jurtshuk P , McEntire JE
DoiPMIDMESH
Adenosine Triphosphatases
Azotobacter
Cell-Free System
Drug Stability
Electron Transport
Enzyme Activation
Freezing
Hydrogen-Ion Concentration
Kinetics
Magnesium
Sonication
Subcellular Fractions
Trypsin
Abstract
The adenosinetriphosphatase (ATPase) (EC 3.6.1.3) activity in Azotobacter vinelandii concentrates in the membranous R3 fraction that is directly associated with Azotobacter electron transport function. Sonically disrupted Azotobacter cells were examined for distribution of ATPase activity and the highest specific activity (and activity units) was consistently found in the particulate R3 membranous fraction which sediments on ultracentrifugation at 144 000 X g for 2 h. When the sonication time interval was increased, the membrane-bound ATPase activity could neither be solubilized nor released into the supernatant fraction. Optimal ATPase activty occurred at pH 8.0; Mg2+ ion when added to the assay was stimulatory. Maximal activity always occurred when the Mg2+:ATP stoichiometry was 1:1 on a molar ratio at the 5 mM concentration level. Sodium and potassium ions had no stimulatory effect. The reaction kinetics were linear for the time intervals studied (0-60 min). The membrane-bound ATPase in the R3 fraction was stimulated 12-fold by treatment wiTH TRypsin, and fractionation studies showed that trypsin treatment did not solubilize ATPase activity off the membranous R3 electron transport fraction. The ATPase was not cold labile and the temperature during the preparation of the R3 fraction had no effect on activity; overnight refrigeration at 4 degrees C, however, resulted in a 25% loss of activity as compared with a 14% loss when the R3 fraction was stored overnight at 25 degrees C. A marked inactivation (although variable, usually about 60%) did occur by overnight freezing (-20 degrees C), and subsequent sonication failed to restore ATPase activity. This indicates that membrane reaggregation (by freezing) was not responsible for ATPase inactivation. The addition of azide, ouabain, 2,4-dinitrophenol, or oligomycin to the assay system resulted in neither inhibition nor stimulation of the ATPase activity. The property of trypsin activation and that ATPase activity is highest in the R3 electron transport fraction suggests that its probable functional role is in coupling of electron transport to oxidative phosphorylation.
Fav
Like
Download
Share
Export
Cite
1.8
Can J Microbiolcanadian journal of microbiology
Metadata
LocationCanada
FromCANADIAN SCIENCE PUBLISHING

No Data

© 2017 - 2020 Medicgo
Powered by some medical students