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Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
Published on: November 22, 2014
The nature of molybdenum-cofactor
Summary
The Neurospora crassa NADPH-nitrate reductase enzyme can be assembled in vitro. This process requires a molybdenum-cofactor, with EDTA playing a crucial role in its stability and formation.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Neurospora crassa NADPH-nitrate reductase (EC1.6.6.2) is essential for nitrate assimilation.
- In vitro assembly of this enzyme has been challenging, requiring specific cofactors.
- Previous work suggested a molybdenum-cofactor is involved in enzyme reconstitution.
Purpose of the Study:
- To investigate the in vitro assembly of Neurospora crassa NADPH-nitrate reductase.
- To elucidate the role of EDTA and other components in molybdenum-cofactor viability and function.
- To provide experimental evidence supporting the nature of the molybdenum-cofactor.
Main Methods:
- Combing the nit-1 mutant of Neurospora crassa with extracts of molybdenum-containing enzymes.
- Utilizing Chelax-100 column chromatography to isolate and analyze cofactor components.
- Assessing cofactor activation using sodium molybdate, EDTA, and reducing agents.
Main Results:
- In vitro assembly of NADPH-nitrate reductase was achieved using a molybdenum-cofactor.
- EDTA is indispensable for molybdenum-cofactor viability and appears to form a complex with molybdenum and labile sulfide.
- The molybdenum-cofactor is of low molecular weight and devoid of protein, consistent with previous predictions.
Conclusions:
- EDTA plays a critical, previously unrecognized role in the stability and function of the molybdenum-cofactor.
- The experimental results strongly support the proposed nature of the molybdenum-cofactor.
- This study provides a foundation for understanding nitrate reductase assembly and cofactor biochemistry.
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