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Multiple regulatory sites in the C‐terminal autoinhibitory domain of the plasma membrane H + ‐ATPase
Author(s) -
Olsson Anne,
Johansson Fredrik,
Sommarin Marianne,
Larsson Christer
Publication year - 1995
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1995.8060959.x
Subject(s) - membrane , lysophosphatidylcholine , atpase , fusicoccin , chemistry , activator (genetics) , biophysics , nicotiana tabacum , biochemistry , enzyme , biology , receptor , phosphatidylcholine , phospholipid , gene
Summary The H + ‐ATPase activities of root and leaf plasma membranes from tobacco ( Nicotiana tabacum ) have been characterized with respect to V max , K m for ATP, pH dependence and activation involving the C‐terminal autoinhibitory domain. With root plasma membranes, addition of lysophosphatidylcholine (lyso‐PC) resulted in the expected increase in V max , a decrease in K m (ATP), and a shift in pH optimum to a more alkaline pH, typical for activation via the C‐terminal inhibitory domain. With leaf plasma membranes, however, K m (ATP) was relatively low and the pH optimum was around pH 7.0 before the addition of lyso‐PC and did not change upon addition of the activator, although V max increased twofold. Similar results were obtained with the in vivo activator fusicoccin. The results obtained with the leaf plasma membranes show that V max may be regulated independently of K m (ATP) and pH optimum, and suggest the presence of at least two regulatory sites within the C‐terminal autoinhibitory domain of the H + ‐ATPase.