Fig. 4
From: Structure of human lysosomal acid α-glucosidase–a guide for the treatment of Pompe disease
rhGAA substrate recognition and specificity and allosteric chaperone binding sites. a Model of isomaltose (steelblue), derived from an overlap with B. obeum α-glucosidase in complex with isomaltose (PDB ID 3MKK), superposed onto the rhGAA-acarbose complex (rmsd of 1.50 Å for 318 aligned Cα positions). b Model of isomaltose bound to rhGAA in surface representation. c The secondary substrate-binding site of rhGAA with unbiased F o –F c difference electron density map calculated before incorporation of acarvosine (orange) into the model and contoured at 2.0 (lightblue) and 3.0 (blue) σ. The surface loop removed by proteolytic treatment is represented by dashed lines. d NAC1 (orange) in the fully occupied binding site. e NAC2 (orange) in the partially occupied binding site. In d and e, unbiased F o –F c difference electron density maps, calculated before incorporation of NAC into the model, are shown in lightblue (2.0 σ) and blue (3.0 σ)
