The molybdenum cofactor biosynthetic protein Cnx1 complements molybdate-repairable mutants, transfers molybdenum to the metal binding pterin, and is associated with the cytoskeleton

被引:77
作者
Schwarz, G [1 ]
Schulze, J [1 ]
Bittner, F [1 ]
Eilers, T [1 ]
Kuper, J [1 ]
Bollmann, G [1 ]
Nerlich, A [1 ]
Brinkmann, H [1 ]
Mendel, RR [1 ]
机构
[1] Tech Univ Braunschweig, Inst Bot, D-38023 Braunschweig, Germany
关键词
D O I
10.1105/tpc.12.12.2455
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
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页码:2455 / 2471
页数:17
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