Dictyostelium calmodulin: affinity isolation and characterization

The Ca2+-binding regulatory protein calmodulin (CaM) has been purified from the cellular slime mold, Dictyostelium discoideum. Isolation of homogeneous Dictyostelium CaM was accomplished in high yield by ion-exchange chromatography and Ca2+-dependent affinity chromatography on phenothiazine-Sepharose 4B. This isolate has been demonstrated to possess the following physicochemical and functional properties characteristic of other CaM isolates: (i) a molecular weight ca. 16,000; (ii) an amino acid composition similar to other CaMs--with the notable exception that Dictyostelium CaM, as first determined by Bazari and Clarke (1981) J. Biol. Chem. 256, 3598-3603] lacks the single trimethylated lysine (Tml) residue identified in nearly all CaMs purified to date; (iii) a CNBr peptide map similar to that of other CaMs; (iv) a Ca2+-dependent shift in migration during native- and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analyses; (v) ability to form Ca2+-dependent complexes with rabbit skeletal muscle troponin I; and (vi) ability to activate in a Ca2+-dependent manner bovine brain cyclic nucleotide phosphodiesterase.