The biosynthetic gene cluster of the maytansinoid antitumor agent ansamitocin from Actinosynnema pretiosum - Yu, T W; Bai, L; Clade, D; Hoffmann, D; Toelzer, S; Trinh, K Q; Xu, J; Moss, S J; Leistner, E; Floss, H G (Proc Natl Acad Sci U.S.A., 2002)