α-(1→2)-Mannosidase I from the endoplasmic reticulum (ERManI), a Family 47 glycoside hydrolase, is a key enzyme in the N-glycan synthesis pathway. Catalytic-domain crystal structures of yeast and human ERMan1s have been determined, the former with a hydrolytic product and the latter without ligands, with the inhibitors 1-deoxymannojirimycin and kifunensine, and with a thiodisaccharide substrate analog. Both inhibitors were bound at the base of the funnel-shaped active site as the unusual 1 C 4 conformer, while the substrate analog glycon is a 3 S 1 conformer. In the current study, AutoDock was used to dock α- d-mannopyranosyl-(1→2)-α- d-mannopyranose with its glycon in chair ( 1 C 4, 4 C 1), half-chair ( 3 H 2, 3 H 4, 4 H 3), skew-boat ( O S 2, 3 S 1, 5 S 1), boat ( 2,5 B, 3,O B, B 1,4, B 2,5), and envelope ( 3 E, 4 E, E 3, E 4) conformations into the yeast ERManI active site. Both docked energies and forces on docked ligand atoms were calculated to determine how the ligand distorts to the transition state. From these, we can conclude that (1) both 1 C 4 and O S 2 can be the starting conformers; (2) the most likely binding pathway is 1 C 4 → 3 H 2 → O S 2 → 3,O B → 3 S 1 → 3 E; (3) the transition state is likely to be close to a 3 E conformation.