The present invention relates to novel nucleic acids which encode novel mutant forms of Inhibitor Protein-1 (I-1). In particular, the I-1 mutant forms comprise altered phosphorylation sites of PKC-α. In addition, the present invention relates to methods of regulating cardiac contractility and function, and for treatment of cardio myopathy and heart failure, which employ the novel nucleic acids and polypeptides. Vectors comprising the novel nucleic acids, Antibodies to the novel proteins, and diagnostic and screening methods associated therewith, are also provided.
