1. Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, U.K.
2. Medical Research Council Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, U.K.
3. Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada