Binding Interaction\nBetween Two Mutant Myocilin Olfactomedin\nDomain Monomers in a Homodimer

In myocilin-associated glaucoma, pathogenic missense\nmutations\naccumulate mainly in the olfactomedin domain (mOLF) of myocilin. This\nmakes the protein susceptible to aggregation, where mOLF–mOLF\ndimerization is possibly an initial stage. Nevertheless, there are\nno molecular level studies that have probed the nature of interactions\noccurring between two mOLF domains and the key characteristics of\nthe resulting dimer complex. In this work, we used AlphaFold2 to obtain\nan I477N mutant mOLF structure with high quality followed by a stable\nI477N mOLF–mOLF homodimer model using molecular docking combined\nwith molecular dynamics simulations. Moreover, molecular mechanics\nPoisson–Boltzmann surface area (MM-PBSA) methods coupled with\nper-residue energy decomposition studies are carried out to identify\nthe key residues involved in the binding interaction. Based on these\nresults, we provide insights into the molecular level understanding\nof the intermolecular interaction between two mOLF domains in an I477N\nhomodimer. Hydrogen bonds, salt bridges, and favorable van der Waals\ninteractions are observed in the binding interface of the homodimer.\nAdditionally, our results suggest that I477N mutant mOLF aggregation\ncould be a multistep process, beginning with an initial mOLF–mOLF\ndimerization mainly mediated by residues such as Asp395 and Arg681.\nAlso, the peptides P1 (residues 326–337) and P3 (residues 426–442)\nof the mOLF domain, previously identified as pertinent for myocilin\naggregation, could potentially contribute to a subsequent stage of\nmyocilin aggregation, the first step being mOLF–mOLF dimerization.