Giardia lamblia: detection and characterization of calmodulin.

Calmodulin was detected in Giardia lamblia by radioimmunoassay and cyclic AMP phosphodiesterase activation. This protein was purified to apparent homogeneity by fast protein liquid chromatography with a yield of 260 ng of calmodulin/mg of protozoan protein. Purity was established by gel electrophoresis, gel filtration, and ion exchange chromatography. The parasite calmodulin has properties characteristic of calmodulin isolated from other eukaryotes, e.g., an apparent molecular weight of 16.7 kD; activation in calcium dependent manner of bovine heart cyclic nucleotide phosphodiesterase; and sensitivity to known calmodulin antagonists.