Conformational gating governs ligand recognition in Bacillus subtilis cytochrome P450 CypX

, the distance from the FG-loop Cα centroid to the heme Fe that reports the cover position over the distal pocket. These descriptors are complemented by reactive-geometry and hydrogen-bond analyses and by MM-PBSA component analysis as a supportive energetic readout. The simulations reveal a conserved mouth-cover landscape with three recurrent basins, open, intermediate, and closed. Ligands mainly redistribute populations across these pre-existing states and reshape gate geometry rather than generating new conformational states. Together, these findings support a conformational-selection mechanism linking ligand recognition, gating, and catalytic readiness in this orphan bacterial P450.