title: Conformational changes in the extracellular beta-lactamase I from Bacillus cereus 569/H/9.
abstract: 1. The thermal denaturation and precipitation of beta-lactamase I from Bacillus cereus 569/H/9 at 60 degrees C are reversible, a soluble and almost fully active enzyme being obtained after solution of the precipitate in 5m-guanidinium chloride or 8m-urea and subsequent removal of the denaturing agent. 2. Inactivation of beta-lactamase I occurs rapidly between 50 degrees and 55 degrees C and is shown by circular-dichroism spectra to be accompanied by an extensive conformational change. 3. A change to a different conformation occurs in 6m-urea. This change is also reversible; refolding with almost complete recovery of enzymic activity occurs within 5min of dilution of the denaturing agent. 4. Inactivation of beta-lactamase I at pH3.0 and 11.0 is also associated with conformational changes, since a proportion of the lost activity is recovered within 5min of adjustment of the pH to 7.0.
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D002942:Circular Dichroism; D003956:Dialysis; D006146:Guanidines; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D010400:Penicillin G; D010405:Penicillinase / Q000032:analysis; D011487:Protein Conformation; D011489:Protein Denaturation; D013696:Temperature; D014508:Urea
chemical_list: D006146:Guanidines; D014508:Urea; D010405:Penicillinase; D010400:Penicillin G