A high-resolution crystal structure of the molybdenum insertase Cnx1E from Arabidopsis thaliana reveals two mutually exclusive molybdate binding sites, that have mechanistic implications for the Mo-insertion process into the pterin moiety of the molybdenum cofactor. In the latest issue of the Biochemical Journal, Kruse et al. found that molybdate is sequentially bound to the entry and the catalytically-productive site, going hand in hand with a distinct backbone conformation shift. In this image, adenylated molybdopterin and the two molybdate ions are shown in front of the Cnx1E active site. (Image provided by J. Krausze, W. A. Sassen and T. Kruse)
