title: Ca-binding to Bacillus licheniformis alpha-amylase (BLA).
abstract: Ca-induced renaturation of Bacillus licheniformis alpha-amylase in the presence of urea has been employed to determine the binding constants of the ion. The native enzyme is folded at 3M urea while the Ca-depleted protein is largely unfolded at this denaturant concentration. Refolding of the protein has been monitored by circular dichroism and the titration curves have been analyzed assuming a model of three independent binding sites. The stoichiometry has been taken from X-ray studies. The refolded protein exhibits a secondary structure that is similar but not identical to that of the native protein. The binding constants have been used to construct a phase diagram that illustrates the contribution of Ca-binding to the resistance against urea unfolding.
authors.affiliation: Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 30, 48149 Münster, Germany.
authors.forename: Ali Reza
authors.initials: AR
authors.lastname: Nazmi
authors.forename: Timm
authors.initials: T
authors.lastname: Reinisch
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Hinz
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D014508:Urea / Q000737:chemistry*; D000516:alpha-Amylases / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D014508:Urea; D000516:alpha-Amylases; C501919:alpha-amylase, Bacillus licheniformis; D002118:Calcium