The molybdenum cofactor (Moco) is a redox active prosthetic group, essentially required for numerous enzyme-catalyzed two electron transfer reactions. Moco is synthesized by an evolutionarily old and highly conserved multistep pathway. In the last step of Moco biosynthesis, the molybdenum center is inserted into the final Moco precursor adenylated molybdopterin (MPT-AMP). This unique and yet poorly characterized maturation reaction finally yields physiologically active Moco. In the model plant Arabidopsis, the two domain enzyme, Cnx1, is required for Moco formation. Recently, a genetic screen identified novel Arabidopsis cnx1 mutant plant lines each harboring a single amino acid exchange in the N-terminal Cnx1E domain. Biochemical characterization of the respective recombinant Cnx1E variants revealed two different amino acid exchanges (S197F and G175D) that impair Cnx1E dimerization, thus linking Cnx1E oligomerization to Cnx1 functionality. Analysis of the Cnx1E structure identified Cnx1E active site-bound molybdate and magnesium ions, which allowed to fine-map the Cnx1E MPT-AMP-binding site.
Structure of the molybdenum insertase Cnx1E domain from the higher plant Arabidopsis thaliana. The structure was solved in complex with molybdate and magnesium ions by X-ray crystallography. Mutational studies identifi ed Cnx1E dimer formation to be essential for substrate binding and hence for the reaction of adenylated molybdopterin (left) and molybdate (center) to molybdenum cofactor (right). For more information see see pp. 163–178 in this issue. Image provided by J. Krausze, W. A. Sassen and T. Kruse
Dimerization of the plant molybdenum insertase Cnx1E is required for synthesis of the molybdenum cofactor
Joern Krausze, Corinna Probst, Ute Curth, Joachim Reichelt, Sayantan Saha, David Schafflick, Dirk W. Heinz, Ralf R. Mendel, Tobias Kruse; Dimerization of the plant molybdenum insertase Cnx1E is required for synthesis of the molybdenum cofactor. Biochem J 1 January 2017; 474 (1): 163–178. doi: https://doi.org/10.1042/BCJ20160846
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