NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Evidence for the Synthesis of ATP by an F0F1 ATP Synthase in Membrane Vesicles from Halorubrum SaccharovorumVesicles prepared in a buffer containing ADP, Mg(2+) and Pi synthesized ATP at an initial rate of 2 nmols/min/mg protein after acidification of the bulk medium (pH 8 (right arrow) 4). The intravesicular ATP concentration reached a steady state after about 30 seconds and slowly declined thereafter. ATP synthesis was inhibited by low concentrations of dicyclohexylcarbodiimide and m-chlorophenylhydrazone indicating that synthesis took place in response to the proton gradient. NEM and PCMS, which inhibit vacuolar ATPases and the vacuolar-like ATPases of extreme halophiles, did not affect ATP synthesis, and, in fact, produced higher steady state levels of ATP. This suggested that two ATPase activities were present, one which catalyzed ATP synthesis and one that caused its hydrolysis. Azide, a specific inhibitor of F0F1 ATP Synthases, inhibited halobacterial ATP synthesis. The distribution of acridine orange as imposed by a delta pH demonstrated that azide inhibition was not due to the collapse of the proton gradient due to azide acting as a protonophore. Such an effect was observed, but only at azide concentrations higher than those that inhibited ATP synthesis. These results confirm the earler observations with cells of H. saccharovorum and other extreme halophiles that ATP synthesis is inconsistent with the operation of a vacuolar-like ATPase. Therefore, the observation that a vacuolar-like enzyme is responsible for ATP synthesis (and which serves as the basis for imputing ATP synthesis to the vacuolar-like ATPases of the extreme halophiles, and the Archaea in general) should be taken with some degree of caution.
Document ID
20020041060
Document Type
Conference Paper
Authors
Faguy, David
(NASA Ames Research Center Moffett Field, CA United States)
Lawson, Darion
(NASA Ames Research Center Moffett Field, CA United States)
Hochstein, Lawrence I.
(NASA Ames Research Center Moffett Field, CA United States)
Chang, Sherwood
Date Acquired
August 20, 2013
Publication Date
January 1, 1996
Subject Category
Life Sciences (General)
Meeting Information
8th International Congress of Bacteriology and Applied Microbiology Meeting(Jerusalem)
Funding Number(s)
PROJECT: RTOP 185-52-32
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
No Preview Available