The crystal structure at pH 4 of the complex of glucoamylase II(471) from Aspergillus awamori var. X100 with the pseudotetrasaccharide D-gluco-dihydroacarbose has been refined to an R-factor of 0.125 against data to 2.2 A resolution. The first two residues of the inhibitor bind at a position nearly identical to those of the closely related inhibitor acarbose in its complex with glucoamylase at pH 6. However, the electron density bifurcates beyond the second residue of the D-gluco-dihydroacarbose molecule, placing the third and fourth residues together at two positions in the active site. The position of relatively low density (estimated occupancy of 35%) corresponds to the location of the third and fourth residues of acarbose in its complex with glucoamylase at pH 6. The position of high density (65% occupancy) corresponds to a new binding mode of an extended inhibitor to the active site of glucoamylase. Presented are possible causes for the binding of D-gluco-dihydroacarbose in two conformations at the active site of glucoamylase at pH 4.
|Journal||F E B S Letters|
|Publication status||Published - 1995|
Stoffer, B., Aleshin, A. E., Firsov, L. M., Svensson, B., & Honzatko, R. B. (1995). Refined structure for the complex of D-gluco-dihydroacarbose with glucoamylase from Aspergillus awamori var. X100 to 2.2 A resolution: dual conformations for extended inhibitors bound to the active site of glucoamylase. F E B S Letters, 358, 57-61. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstract&list_uids=7821430&query_hl=29&itool=pubmed_docsum