[1] NCI, Lab Cellular & Mol Biol, Bethesda, MD 20892 USA
[2] NCI, Cell Biol Lab, Bethesda, MD 20892 USA
[3] NHLBI, Lab Mol Physiol, NIH, Bldg 10, Bethesda, MD 20892 USA
[4] NHLBI, Cardiovasc & Pulm Branch, NIH, Bldg 10, Bethesda, MD 20892 USA
[5] Grinnell Coll, Dept Biol, Grinnell, IA 50112 USA