J. Biol. Chem., Vol. 258, Issue 20, 12110-12113, Oct, 1983
A monoclonal antibody showing cross-reactivity toward three calmodulin- dependent enzymes
KC Wang, HY Wong, JH Wang and HY Lam
The spleen cells of a Balb/c mouse immunized with purified bovine
calmodulin-dependent cyclic nucleotide phosphodiesterase were fused with
nonsecreting mouse myeloma cells (P3-X63-Ag8-653). Antibody producing
hybridomas were screened by the enzyme-linked immunosorbent assay using
purified phosphodiesterase as the antigen. One monoclonal cell line, CR-B1,
was found to produce antibodies which showed positive enzyme-linked
immunosorbent assay reactions with bovine brain calcineurin and rabbit
muscle phosphorylase kinase in addition to phosphodiesterase. The antibody
was purified and characterized. It was shown to immunoprecipitate the
calmodulin (CaM)-dependent phosphodiesterase and phosphorylase kinase
activities but not those of CaM itself, CaM-independent phosphodiesterase
and the catalytic unit of cAMP-dependent protein kinase. The
immunoprecipitation of phosphodiesterase could be inhibited by calcineurin
and phosphorylase kinase. These results suggest that the antibody interacts
at a common site on these calmodulin-dependent proteins. The antigenic
determinant in phosphodiesterase does not appear to reside in the
calmodulin- binding domain of the enzyme since the antibody and
phosphodiesterase interaction is not inhibited by calmodulin, and the
calmodulin activation of phosphodiesterase is not affected by CR-B1
antibody. It is therefore suggested that the structural similarity among
the three calmodulin-dependent proteins extends beyond the
calmodulin-binding domains.