JBC, Vol. 252, Issue 10, 3357-3363, May, 1977
Characterization of plasma membrane adenosine triphosphatase of Neurospora crassa
B. J. Bowman and C. W. Slayman
It has been proposed (Slayman, C.L., Long W.S., and Lu, C.Y.-H. (1973) J.
Membr. Biol. 14, 305--338) that in Neurospora crassa, a plasma membrane
ATPase functions to pump H+ ions out of the cell, thereby generating an
electrochemical gradient that can drive transport processes. Using the
concanavalin A method of Scarborough (Scarborough G.A. (1975)J. Biol. Chem.
250, 1106--1111), we have prepared plasma membranes of Neurospora and have
deomonstrated that they do contain a distinct ATPase activity with the
following properties. It has a pH optimum of 6.0, is highly specific for
ATP (hydrolyzing other nucleoside triphosphates less than 6% as rapidly),
requires Mg2+ at concentrations approximately equimolar to the
concentration of ATP, is weakly stimulated by certain monovalent cations
(K+ and NH4+) and anions (SCN- and acetate), is inhibited by
N,N'-dicyclohexylcarbodiimide, but is not affected by oligomycin or
ouabain. The plasma membrane fraction also contains residual mitochondrial
contamination, which can be determined quantitatively by assaying
oligomycin-sensitive ATP-ase activity, at pH 8.25, and succinic
dehydrogenase activity.
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