1. Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region 142290 Russia, Department of Biochemistry and Pharmacy, Åbo Akademi University, Artillerigatan 6, P.O. Box 66, FIN-20521 Turku, Finland, Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Pushchino, Moscow region 142290 Russia, and Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202