1. J. Drgonová, T. Drgon, R. Kollár, R. A. Ford, E. Cabib, Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, Building 10, Room 9N-115, Bethesda, MD 20892, USA.
2. K. Tanaka and Y. Takai, Department of Molecular Biology and Biochemistry, Osaka University Medical School, 2-2 Yamada-oka, Suita, Osaka 565, Japan.
3. G.-C. Chen and C. S. M. Chan, Department of Microbiology, University of Texas, Austin, TX 78712, USA.