Naphthylphthalamic acid-binding sites in cultured cells from Nicotiana tabacum |
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Authors: | A C Maan B Kühnel J J B Beukers K R Libbenga |
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Institution: | (1) Department of Plant Molecular Biology, Botanisch Laboratorium, Rijksuniversiteit, Nonnensteeg 3, NL-2311 VJ Leiden, The Netherlands;(2) Present address: University of Health Sciences/The Chicago Medical School, 3333 Green Bay Road, 60064 North Chicago, IL, USA |
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Abstract: | Naphthylphthalamic acid (NPA), an inhibitor of polar auxin transport, binds with high affinity to membrane preparations from callus and cell suspension cultures derived from Nicotiana tabacum (K
d
approx. 2·10–9 M). The concentration of membrane-bound binding sites is higher in cell suspension than in callus cultures. The binding of NPA to these sites seems to be a simple process, in contrast to the binding of the synthetic auxin naphthylacetic acid (1-NAA) to membrane preparations from callus cultures, which is more complex (A.C. Maan et al., 1983, Planta 158, 10–15). Naphthylacetic acid, a number of structurally related compounds and the auxin-transport inhibitor triiodobenzoic acid were all able to compete with NPA for the same binding site with K
d
values ranging from 10–6 to 10–4 M. On the other hand, NPA was not able to displace detectable amounts of NAA from the NAA-binding site. A possible explantation is the existence of two different membrane-bound binding sites, one exclusively for auxins and one for NPA as well as auxins, that differ in concentration. The NPA-binding site is probably an auxin carrier.Abbreviations 1-NAA
1-Naphthylacetic acid
- 2-NAA
2-Naphthylacetic acid
- NPA
N-1-Naphthylphthalamic acid |
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Keywords: | Auxin (binding) Cell culture (hormone binding) Naphthylphthalamic acid Nicotiana (auxin binding) |
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