1. The Hormel Institute, University of Minnesota, 801 16th Avenue NE Austin, Minnesota 55912, USA, Institut de Biochimie et de Génétique Cellulaires, CNRS-UMR 5095, 1 rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France, and The Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya str., 16/10, 117871 Moscow, GSP-7 V-437 Russia