Auxin Receptors and Auxin Binding Proteins |
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Authors: | Michal A. Venis Richard M. Napier Dr. Winslow R. Briggs |
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Affiliation: | 1. Horticulture Research International , East Malling, West Malling, Kent, ME19 6BJ, U.K.;2. Dept. of Plant Biology , Carnegle Institution of Washington , 290 Panama Street, Stanford, CA, 94305–1297, USA |
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Abstract: | In the last few years, a large number of auxin-binding proteins (ABPs) have been reported. Implicitly or explicitly, interest in such proteins resides in their possible role as auxin receptors. Many of these proteins are characterized as ABPs solely by their susceptibility to covalent photolabeling by tritiated azido-indole-3-acetic acid. In most cases where the labeled polypeptides have been identified, they turn out to have roles unconnected with primary auxin perception. It seems likely that auxin is binding to sites of catholic specificity in these cases and the influence of experimental protocols on the data is discussed. Because the term ABP implies that auxin binding affects the function of that protein, the importance of establishing further criteria before photolabeled peptides can be termed ABPs is emphasized. Applying such criteria, only a very few ABPs are currently of interest and only one of these, maize ABP1, has been characterized in detail. This protein is located primarily within the lumen of the endoplasmic reticulum, although an important fraction appears to function on the outside of the plasma membrane. The protein has a wide species distribution and it now seems highly probable that it is a genuine auxin receptor, the only protein for which such a function has yet been established. This conclusion is based on three independent lines of electrophysiological evidence, together with confocal imaging of cytoplasmic pH changes. |
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Keywords: | endoplasmic reticulum plasma membrane membrane potential patch clamp ion channels photolabeling |
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