Molecular Dynamics Simulations of Phytopthora sojae Avirulence Factor 5, PsAvh5, Define Membrane Binding and Inositolphosphate-3'-phosphate Interactions and Protein Mechanics

Phytopthora Avirulence proteins are a primary target for development of rational chemical and biological control of some of the most devastating plant pathogens. Despite the sequencing of entire genomes, and characterization of many of these proteins at the chemical level, many questions remain regarding actual chemical and biological interactions involved. In addition, disputed roles of ligands, such as Inositolphosphate-3-phosphate and amino acids of important function remain unclear. To address some of these issues, we developed molecular models from structural elements and published data for Phytopthora sojae avirulence protein 5. Molecular dynamics simulations are used to study protein function, interactions involved primarily with lipids and membranes, and inositol derivatives. Our findings indicate that the protein is stable as a monomer, and in a dimeric form. Also, that these proteins interact with Inositolphosphate-3phosphate as a necessary membrane element, in binding. We identified several amino acids of importance, additional to defining the mechanical features of the protein within the binding process to different membranes. A high affinity, comparable to other membrane surface binding molecules of -219.54 Kcal for the dimer, and -176.61 for the monomer were determined. With either form, we found the inositolphosphate-3-phosphate to be essential in the membrane binding process. Our findings answer some of the debated questions while creating a point to further test avirulence proteins in general for functional aspects. Additionally, the structures and data can be utilized to provide a better starting point for rational design approaches to control this pathogen.