Two-Amino Acid Molecular Switch in an Epithelial Morphogen That Regulates Binding to Two Distinct Receptors - Yan, Minhong; Wang, Li-Chong; Hymowitz, Sarah G.; Schilbach, Sarah; Lee, James; Goddard, Audrey; de Vos, Abraham M.; Gao, Wei-Qiang; Dixit, Vishva M. (Science, 2000)