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Phosphorylation and Calcium Binding Properties of an Arabidopsis GF14 Brain Protein Homolog

Guihua Lu, Paul C. Sehnke and Robert J. Ferl
The Plant Cell
Vol. 6, No. 4 (Apr., 1994), pp. 501-510
DOI: 10.2307/3869930
Stable URL: http://www.jstor.org/stable/3869930
Page Count: 10
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Phosphorylation and Calcium Binding Properties of an Arabidopsis GF14 Brain Protein Homolog
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Abstract

Arabidopsis GF14ω was originally described because of its apparent association with a DNA-protein complex; it is a member of the 14-3-3 kinase regulatory protein family that is conserved throughout eukaryotes. Here, we demonstrated that recombinant GF14ω is expressed in Escherichia coli as a dimer. Blot binding and electrophoretic mobility shift analyses indicated that GF14ω binds calcium. Equilibrium dialysis further demonstrated that GF14ω binds an equimolar amount of calcium with an apparent binding constant of $5.5\times 10^{4}\ {\rm M}^{-1}$ under physiological conditions. The C-terminal domain, which contains a potential EF hand motif, is responsible for the calcium binding. The C-terminal domain also cross-reacted with the anti-GF14ω monoclonal antibody. In addition, GF14ω is phosphorylated by Arabidopsis protein kinase activity at a serine residue(s) in vitro. Therefore, GF14ω protein has biochemical properties consistent with potential signaling roles in plants. The presence of a potential EF hand-like motif in the highly conserved C terminus of 14-3-3 proteins together with the calcium-dependent multiple functions attributed to the 14-3-3 proteins indicate that the C terminus EF hand is a common functional element of this family of proteins.

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