1. Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Medical School, Minneapolis, Minnesota 55455, Edward Via Virginia College of Osteopathic Medicine, Blacksburg, Virginia 24060, Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland 21201, and Division of Cardiology, Department of Medicine, Johns Hopkins University, 720 Rutland Avenue/Ross 858, Baltimore, Maryland 21205