1. Department of Proteomics and Signal Transduction, Max-Planck-Institute for Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101300, China, and Proxeon Biosystems A/S, Stærmosegårdsvej 6, 5230 Odense, Denmark