A model for the interaction between plant GAPN and 14-3-3ζ using protein-protein docking calculations, electrostatic potentials and kinetics

Phosphorylated non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.9; GAPN) found in heterotrophic cells of wheat is activated by MgCl2. The divalent cation disrupts the interaction between GAPN and a 14-3-3 regulatory protein. This effect is quite remarkable, since it has previously been shown that 14-3-3 binding to a target protein requires divalent cations as Mg2+ or Ca2+. Binding of the divalent cation to 14-3-3 causes an increase in surface hydrophobicity. Crystal structure of a 14-3-3-target protein complex has been only determined for serotinin N-acetyltransferase. We utilized a model of a subunit of plant GAPN and the crystallographic structure of human 14-3-3ζ to shape the complex between theses two proteins. Initial dockings were performed with the BiGGER program, which allows an exhaustive search of translational and rotational space. A filtering procedure was then applied to reduce the number of complexes to a manageable number. We predict the structural characteristics of GAPN-14-3-3ζ binding process, proposing that the main attractive force in this complex derives from electrostatic interactions. The predicted model was corroborated by analysis of kinetic behavior of GAPN and its relationship with pH and ionic strength conditions. This study provides a variant on the interaction of 14-3-3 with target proteins, thus affording a wider scenario to establish possible structural models for this remarkable family of regulatory proteins.