Auxin-stimulated ATPase in membrane fractions from pumpkin hypocotyls (Cucurbita maxima L.) |
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Authors: | Günther F E Scherer |
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Institution: | (1) Botanisches Institut, Universität Bonn, Venusbergweg 22, D-5300 Bonn 1, Federal Republic of Germany |
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Abstract: | Membrane fractions from Cucurbita maxima hypocotyls were isolated in a medium which inhibits the action of endogenous phospholipases. After removal of soluble phosphatases by Sepharose 2B-CL column chromatography, an auxin-stimulated ATPase activity was found in membrane fractions from linear sucrose gradients. In the presence of 10-4 M phenylacetic acid (PAA), the stimulation by indol-3-acetic acid (IAA) exhibited a bimodal concentration dependence with maximal stimulation of about 50% at 10-6 M IAA. Without PAA, only a high concentration of 10-4 M IAA was stimulatory, whereas 10-6 M IAA had no apparent effect and 10-8 M IAA exhibited weak inhibition. PAA alone had only weak or no effects. The effects of IAA must be considered as hormone-specific. The ATPase activity in the presence of 10-4 M PAA was activated only by 2,4-dichlorophenoxyacetic acid (2,4-D), an active auxin analogue, but not by the inactive stereoisomers, 2,3-D and 3,5-D. Comparison with marker enzyme profiles suggested that part of the auxin-stimulated ATPase was localized on plasma membranes as well as other compartments. Thus, the auxin-stimulated ATPase may become a useful tool in the investigation of the mechanism of action of auxin.Abbrevations 2,4-D
2,4-dichlorophenoxyacetic acid
- 2,3-D
2,3-dichlorophenoxyacetic acid
- 3,5-D
3,5-dichlorophenoxyacetic acid
- IAA
indol-3-acetic acid
- PAA
phenylacetic acid
- MES
(2-(N-morpholino))-ethanesulfonic acid
- EDTA
ethylenediamine tetraacetic acid |
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Keywords: | ATPase Auxin Cucurbita Hypocotyl Membrane fractionation |
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