1 Freie Universität Berlin, Institute for Biology/Genetics, Takustraße 6, 14195, Berlin, Germany. Electronic address: stephan.sigrist@fu-berlin.de.
2 Department of Biochemistry, Graduate School of Medicine/Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan. Electronic address: tohtsuka@yamanashi.ac.jp.