1O8Q

The active site of the molybdenum cofactor biosenthetic protein domain Cnx1G

Summary for 1O8Q

• Entry DOI: 10.2210/pdb1o8q/pdb
• Related: 1EAV 1O8N 1O8O
• Descriptor: MOLYBDOPTERIN BIOSYNTHESIS CNX1 PROTEIN (2 entities in total)
• Functional Keywords: molybdenum cofactor biosynthesis, cnx1g, mutants
• Biological source: ARABIDOPSIS THALIANA (MOUSE-EAR CRESS)
• Total number of polymer chains: 8
• Total formula weight: 141596.14

Authors

Kuper, J.,Winking, J.,Hecht, H.J.,Schwarz, G.,Mendel, R.R. (deposition date: 2002-11-28, release date: 2003-02-27, Last modification date: 2023-12-13)

Primary citation

Kuper, J.,Winking, J.,Hecht, H.J.,Mendel, R.R.,Schwarz, G.
The Active Site of the Molybdenum Cofactor Biosynthetic Protein Domain Cnx1G
Arch.Biochem.Biophys., 411:36-, 2003

PubMed Abstract: 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.

PubMed: 12590921
DOI: 10.1016/S0003-9861(02)00714-2

Experimental method

X-RAY DIFFRACTION (2.6 Å)