Membrane-Bound Transcription Factor Site-1 Protease in PF429242 Bound State: Computational Kinetics and Dynamics of Reversible Binding.

Membrane-bound transcription factor site-1 protease (S1P) is an emerging clinical target due to its roles in lipogenesis, lysosomal biogenesis, unfolded protein response and viral glycoprotein processing. In this study, homology model of S1P was created in order to understand the structural basis for S1P inhibition by PF429242 using molecular docking, molecular dynamics simulation and in silico kinetics studies. PF429242 was docked (GlideScore=-5.20 kcal/mol) into the catalytic triad (D218, H249 and S414) and validated (R=0.5686). The reversible binding kinetic parameter (K/K) was estimated at=7.28E- M with fully bound and apo-states interspersed by 3 transient ligand-bound states with unique binding signatures; water plays a major role in PF429242 dissociation from the catalytic site. Communication between key catalytic triad residues is altered in the presence of PF429242. In apo-S1P state, S414-S307/V216-D218 is the preferred route but in PF429242-bound state, S414-S417/V216-D218 is preferred. Communication between S414 and H249 is also shortened in PF429242 bound state; here, only L410 is required unlike apo-state, which requires P418, V256 and F252. Ligand binding did not alter the communication route between S414 and H249 as both recruited D244 and G220. In conclusion, PF429242 binds tightly but reversible to S1P and the details of this interaction has been presented to guide future efforts at developing novel inhibitors. Site-1-protease; PF429242; Kon/Koff; Network analysis.