Presence of calmodulin-like calcium-binding protein in Bacillus cereus T spores

Abstract Bacillus cereus T spores were extensively washed, broken, and heated at 90°C for 2 min. Using calcium-dependent hydrophobic interaction chromatography, a single peak protein fraction was obtained which possessed calcium-binding capacity and some characteristics of calmodulin. This heat-stable protein fraction was retained by hydrophobic matrices (Phenyl-Sepharose) or a calmodulin antagonist (naphthalenesulfonamide) in a calcium-dependent manner. Calcium binding ability was verified by ⁴⁵Ca autoradiography and a competitive calcium binding assay using Chelex-100. The crude spore extract displaced bovine brain calmodulin from its antibody in a radioimmunoassay and the immunoreactive specific activity of the partially purified fraction was approx. 200-fold greater than the crude spore extract. Thus, B. cereus T spores have a calcium-binding protein with calmodulin-like properties.