|
Plant Cell, Vol. 12, 2455-2472, December 2000, Copyright © 2000, American Society of Plant Physiologists
The Molybdenum Cofactor Biosynthetic Protein Cnx1 Complements Molybdate-Repairable Mutants, Transfers Molybdenum to the Metal Binding Pterin, and Is Associated with the Cytoskeleton
Günter Schwarza,
Jutta Schulzea,
Florian Bittnera,
Thomas Eilersa,
Jochen Kupera,
Gabriele Bollmanna,
Andrea Nerlicha,
Henner Brinkmanna, and
Ralf R. Mendela
a Botanical Institute, Technical University of Braunschweig, 38023 Braunschweig, Germany
Correspondence to:
Ralf R. Mendel, R.Mendel{at}tu-bs.de (E-mail), 49-531-391-8128 (fax)
Molybdenum (Mo) plays an essential role in the active site of all eukaryotic Mo-containing enzymes. In plants, Mo enzymes are important for nitrate assimilation, phytohormone synthesis, and purine catabolism. Mo is bound to a unique metal binding pterin (molybdopterin [MPT]), thereby forming the active Mo cofactor (Moco), which is highly conserved in eukaryotes, eubacteria, and archaebacteria. Here, we describe the function of the two-domain protein Cnx1 from Arabidopsis in the final step of Moco biosynthesis. Cnx1 is constitutively expressed in all organs and in plants grown on different nitrogen sources. Mo-repairable cnxA mutants from Nicotiana plumbaginifolia accumulate MPT and show altered Cnx1 expression. Transformation of cnxA mutants and the corresponding Arabidopsis chl-6 mutant with cnx1 cDNA resulted in functional reconstitution of their Moco deficiency. We also identified a point mutation in the Cnx1 E domain of Arabidopsis chl-6 that causes the molybdate-repairable phenotype. Recombinant Cnx1 protein is capable of synthesizing Moco. The G domain binds and activates MPT, whereas the E domain is essential for activating Mo. In addition, Cnx1 binds to the cytoskeleton in the same way that its mammalian homolog gephyrin does in neuronal cells, which suggests a hypothetical model for anchoring the Moco-synthetic machinery by Cnx1 in plant cells.
This article has been cited by other articles:

|
 |

|
 |
 
B. Smolinsky, S. A. Eichler, S. Buchmeier, J. C. Meier, and G. Schwarz
Splice-specific Functions of Gephyrin in Molybdenum Cofactor Biosynthesis
J. Biol. Chem.,
June 20, 2008;
283(25):
17370 - 17379.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
A. Llamas, T. Otte, G. Multhaup, R. R. Mendel, and G. Schwarz
The Mechanism of Nucleotide-assisted Molybdenum Insertion into Molybdopterin: A NOVEL ROUTE TOWARD METAL COFACTOR ASSEMBLY
J. Biol. Chem.,
July 7, 2006;
281(27):
18343 - 18350.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
A. Llamas, R. R. Mendel, and G. Schwarz
Synthesis of Adenylated Molybdopterin: AN ESSENTIAL STEP FOR MOLYBDENUM INSERTION
J. Biol. Chem.,
December 31, 2004;
279(53):
55241 - 55246.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
I. S. Heck, J. D. Schrag, J. Sloan, L. J. Millar, G. Kanan, J. R. Kinghorn, and S. E. Unkles
Mutational Analysis of the Gephyrin-Related Molybdenum Cofactor Biosynthetic Gene cnxE From the Lower Eukaryote Aspergillus nidulans
Genetics,
June 1, 2002;
161(2):
623 - 632.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
T. Eilers, G. Schwarz, H. Brinkmann, C. Witt, T. Richter, J. Nieder, B. Koch, R. Hille, R. Hansch, and R. R. Mendel
Identification and Biochemical Characterization of Arabidopsis thaliana Sulfite Oxidase. A NEW PLAYER IN PLANT SULFUR METABOLISM
J. Biol. Chem.,
December 7, 2001;
276(50):
46989 - 46994.
[Abstract]
[Full Text]
[PDF]
|
 |
|
|
|