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Abstract Detail



Biochemistry, metabolism, carbon flux

Labandera, Anne-Marie [1], Uhrig, R. Glen [2], Moorhead, Greg [1].

Identification and biochemical characterization of a new class of tyrosine phosphatase in plants.

The study of tyrosine phosphorylation in plants has been neglected due to the lack of classic tyrosine kinases and tyrosine phosphatases. However, thanks to advanced phosphoproteomics studies, it has been revealed that the abundance of phospho-tyrosine residues in plants rivals humans. This strongly suggests that in plants tyrosine phosphorylation is as important as in humans, yet we know nothing about the players responsible of these events. The Arabidopsis thaliana Rhizobiales-like phosphatase 2 (AtRLPH2) is a novel protein phosphatase, not found in mammals which, according to bioinformatics analysis, clusters with the serine/threonine specific phospho-protein phosphatase (PPP) group. AtRLPH2 has not been characterized however, we have demonstrated in vitro that the recombinant AtRLPH2 surprisingly behaves like a tyrosine phosphatase. AtRLPH2 is not affected by the classic PPP inhibitors but in turn it was shown to be inhibited by the specific tyrosine phosphatase inhibitor, sodium orthovanadate. Moreover, AtRLPH2 dephosphorylates phospho-tyrosine peptides having essentially no activity towards phospho-serine/threonine residues. To support the phospho-tyrosine phosphatase nature of the bacterially expressed AtRLPH2, the endogenous AtRLPH2 from Arabidopsis thaliana was purified by immunoprecipitation and was indeed shown to preferentially dephosphorylate tyrosine phosphorylated peptides. Furthermore, a 56 kDa protein, which is heavily tyrosine phosphorylated and is commonly used in human phospho-tyrosine phosphatase studies (GST-Fer), was also readily dephosphorylated by the endogenous AtRLPH2. This is the first example of a supposed serine/threonine specific phosphatase that behaves as a tyrosine phosphatase in plants. To gain a better understanding of AtRLPH2 significance and targets, a phosphoproteomics study is currently being undertaken to compare tyrosine phosphorylated peptides from wild type (WT) and atrlph2 knock out plant lines. Finally, a preliminary phenotypical study has shown that seeds lacking AtRLPH2 germinate faster than WT plants under standard conditions suggesting AtRLPH2 involvement in repressing the initiation of germination.


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1 - University of Calgary, Biological Sciences, 2500 University Drive N.W., Calgary, AB, T2N 1N4, Canada
2 - ETH Zurich, Department of Biology, Universitatstrasse 2, LFW Building, Zurich, 8092, Switzerland

Keywords:
Phosphorylation
Arabidopsis
Phosphoproteomics.

Presentation Type: Oral Paper:Papers for Topics
Session: 43
Location: Hall A/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:45 AM
Number: 43003
Abstract ID:249
Candidate for Awards:CSPB President's Award for Best Student Presentation


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