1. Department of Cell Biology (H.S.C., T.L.), Parke-Davis Pharmaceutical Research Division, Warner-Lambert Co., Ann Arbor, Michigan 48105;
2. Department of Molecular Biology (S.R.T.), Parke-Davis Pharmaceutical Research Division, Warner-Lambert Co., Ann Arbor, Michigan 48105;
3. Department of Biological Chemistry, University of Michigan Medical School (T.L.), Ann Arbor, Michigan 48109