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| {{STRUCTURE_1o8q| PDB=1o8q | SCENE= }} | | {{STRUCTURE_1o8q| PDB=1o8q | SCENE= }} |
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| '''THE ACTIVE SITE OF THE MOLYBDENUM COFACTOR BIOSENTHETIC PROTEIN DOMAIN CNX1G'''
| | ===THE ACTIVE SITE OF THE MOLYBDENUM COFACTOR BIOSENTHETIC PROTEIN DOMAIN CNX1G=== |
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| ==Overview==
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| 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. | | The line below this paragraph, {{ABSTRACT_PUBMED_12590921}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12590921 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12590921}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Molybdenum cofactor biosynthesis]] | | [[Category: Molybdenum cofactor biosynthesis]] |
| [[Category: Mutant]] | | [[Category: Mutant]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 03:31:47 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 13:17:52 2008'' |