... in the substrate-binding domain andstrand E2 in the hinge domain, two residues appear toact, at least partly, as structural determinants for the closed conformation of the substrate loop. The ... positioning of the aromatic ring of Tyr456 in the closed state. In the absence of a closed complex of E542K P2Ox, the effect of the loss of this hydrogen bond on the packing of the substrate loop ... 2IGO, the largest difference observed is the position of the ‘head’ domain (Fig. 8). In the thermostable L537W ⁄ E542Kdouble mutant, differences in the backbone position of the exposed head domain...