1o8q
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THE ACTIVE SITE OF THE MOLYBDENUM COFACTOR BIOSENTHETIC PROTEIN DOMAIN CNX1G
OverviewOverview
The final step of molybdenum cofactor biosynthesis in plants is catalyzed, by the two-domain protein Cnx1. The G domain of Cnx1 (Cnx1G) binds, molybdopterin with high affinity and transfers molybdenum to, molybdopterin. Here, we describe the functional and structural, characterization of structure-based Cnx1G mutants. For molybdopterin, binding residues Thr542 and Ser573 were found to be important because, different mutations of those residues resulted in 7- to 26-fold higher, k(D) values for molybdopterin binding. Furthermore, we showed that the, terminal phosphate of molybdopterin is directly involved in protein-pterin, interactions as dephosphorylated molybdopterin binds with one magnitude of, order lower affinity to the wild-type protein. Molybdopterin binding was, not affected in mutants defective in Ser476, Asp486, or Asp515. However, molybdenum insertion was completely abolished, indicating their important, role for catalysis. Based on these results we propose the binding of, molybdopterin to a large depression in the structure of Cnx1G formed by, beta5, alpha5, beta6, and alpha6, whereas the negatively charged, depression formed by the loop between beta3 and alpha4, the N-terminal end, of alpha2, the 3(10) helix, and the region between beta6 and alpha6 is, involved in catalysis.
About this StructureAbout this Structure
1O8Q is a Single protein structure of sequence from Arabidopsis thaliana. Full crystallographic information is available from OCA.
ReferenceReference
The active site of the molybdenum cofactor biosynthetic protein domain Cnx1G., Kuper J, Winking J, Hecht HJ, Mendel RR, Schwarz G, Arch Biochem Biophys. 2003 Mar 1;411(1):36-46. PMID:12590921
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