Structure-Function Analysis of the Presumptive Arabidopsis Auxin Permease AUX1

Swarup, Ranjan, Kargul, Joanna, Marchant, Alan, Zadik, Daniel, Rahman, Abidur, Mills, Rebecca, Yemm, Anthony, May, Sean, Williams, Lorraine, Millner, Paul, Tsurumi, Seiji, Moore, Ian, Napier, Richard, Kerr, Ian D. and Bennett, Malcolm J. (2004) Structure-Function Analysis of the Presumptive Arabidopsis Auxin Permease AUX1. The Plant Cell, 16, (11), 3069-3083. (doi:10.1105/tpc.104.024737).


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We have investigated the subcellular localization, the domain topology, and the amino acid residues that are critical for the function of the presumptive Arabidopsis thaliana auxin influx carrier AUX1. Biochemical fractionation experiments and confocal studies using an N-terminal yellow fluorescent protein (YFP) fusion observed that AUX1 colocalized with plasma membrane (PM) markers. Because of its PM localization, we were able to take advantage of the steep pH gradient that exists across the plant cell PM to investigate AUX1 topology using YFP as a pH-sensitive probe. The YFP-coding sequence was inserted in selected AUX1 hydrophilic loops to orient surface domains on either apoplastic or cytoplasmic faces of the PM based on the absence or presence of YFP fluorescence, respectively. We were able to demonstrate in conjunction with helix prediction programs that AUX1 represents a polytopic membrane protein composed of 11 transmembrane spanning domains. In parallel, a large aux1 allelic series containing null, partial-loss-of-function, and conditional mutations was characterized to identify the functionally important domains and amino acid residues within the AUX1 polypeptide. Whereas almost all partial-loss-of-function and null alleles cluster in the core permease region, the sole conditional allele aux1-7 modifies the function of the external C-terminal domain.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1105/tpc.104.024737
ISSNs: 1040-4651 (print)
Related URLs:
Subjects: S Agriculture > SB Plant culture
Divisions : University Structure - Pre August 2011 > School of Biological Sciences
ePrint ID: 35546
Accepted Date and Publication Date:
14 October 2004Published
4 June 2004Submitted
Date Deposited: 18 May 2006
Last Modified: 31 Mar 2016 12:03

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