Poster abstracts
Poster number 78 submitted by Will Higgins
Quasi-Ordered Recognition Dynamics in Sperm-Egg Interactions in Abalone
William T. Higgins (The Ohio State University), Damien B. Wilburn (The Ohio State University)
Abstract:
Protein evolution does not occur at a fixed rate over time, but rather as a dynamic process influenced by physiological and genetic factors. Some protein sites are subject to higher degrees of evolutionary conservation than others, such as catalytic residues or residues involved in forming protein-protein interactions. In the marine mollusk abalone, sperm lysin and egg VERL are rapidly coevolving proteins that mediate species-specific interactions during fertilization. The VERL binding interface on lysin consists of many rapidly evolving residues that are loosely packed in a “quasi-ordered” state that is primarily stabilized by the coordination an aromatic triad: W3, W62, Y133. This hydrophobic packing is observed in red abalone and closely related taxa, but Y133 is a derived characteristic compared to ancestral N133. This evolutionary transition coincides with a Q63A mutation adjacent to W62. The precise interactions and dynamics between these residues are not well understood. We employed molecular dynamics simulations using hydrogen mass repartitioning to evaluate the effects of A63Q and Y133N mutations in red abalone lysin to gain further insights about the protein dynamics on longer timescales. Preliminary analyses support that epistatic constraints have preserved this spatial coordination via these residues through alternative molecular interactions. Complementary solution NMR experiments to evaluate these trends are ongoing. Few quasi-ordered proteins have been biophysically characterized, and patterns inferred from lysin structural evolution to maintain species-specific fertilization may provide useful insights into other protein systems with complex molecular dynamics.
Keywords: Molecular Dynamics, Protein Evolution, Coevolution