A Predicted Structure of the Angiomotin Lipid Binding Domain

Abstract

Amots are a family of adapter proteins that modulate cellular polarity, differentiation, proliferation, and migration. Amot family members also have a characteristic lipid-binding domain, the coiled coil homology (ACCH) Domain that selectively targets the protein to membranes, which has been directly linked to its regulatory role in the cell. Therefore, we endeavored to understand the structure-function relationship of this domain with the desire to find ways to modulate these signaling pathways. After many failed attempts to crystallize the ACCH domain of each of the Amot family members for structural analysis, we decided to pursue homologous models that could be refined using small angle x-ray scattering data. Theoretical models were produced using the Zhang suite programs I-TASSER and LOMETS and then refined and analyzed using Coot and PyMol modeling software based on RMSD, C-score, TM-score, and template redundancy. Top models were then compared to SAXS data for further model selection and refinement. As a result, we present a theoretical model of the domain that is driven by alpha helices and short random coil regions. These alpha helical regions form a classic dimer interface followed by two wide spread legs that we predict to be the lipid binding interface. Finally, we validate the model presented with several lipid binding assays, which leads to a suggested mechanism that links ACCH lipid binding, membrane deformation, and vesicle fusion functions.