NarJ is a specific chaperone required for molybdenum cofactor assembly in nitrate reductase A of Escherichia coli
- 1 April 1998
- journal article
- research article
- Published by Wiley in Molecular Microbiology
- Vol. 28 (3), 435-447
- https://doi.org/10.1046/j.1365-2958.1998.00795.x
Abstract
The formation of active membrane‐bound nitrate reductase A in Escherichia coli requires the presence of three subunits, NarG, NarH and NarI, as well as a fourth protein, NarJ, that is not part of the active nitrate reductase. In narJ strains, both NarG and NarH subunits are associated in an unstable and inactive NarGH complex. A significant activation of this complex was observed in vitro after adding purified NarJ‐6His polypeptide to the cell supernatant of a narJ strain. Once the apo‐enzyme NarGHI of a narJ mutant has become anchored to the membrane via the NarI subunit, it cannot be reactivated by NarJ in vitro. NarJ protein specifically recognizes the catalytic NarG subunit. Fluorescence, electron paramagnetic resonance (EPR) spectroscopy and molybdenum quantification based on inductively coupled plasma emission spectroscopy (ICPES) clearly indicate that, in the absence of NarJ, no molybdenum cofactor is present in the NarGH complex. We propose that NarJ is a specific chaperone that binds to NarG and may thus keep it in an appropriate competent‐open conformation for the molybdenum cofactor insertion to occur, resulting in a catalytically active enzyme. Upon insertion of the molybdenum cofactor into the apo‐nitrate reductase, NarJ is then dissociated from the activated enzyme.Keywords
This publication has 41 references indexed in Scilit:
- Lounging in a lysosome: the intracellular lifestyle of Coxiella burnetiiCellular Microbiology, 2007
- Molybdenum Cofactor BiosynthesisPublished by Elsevier BV ,1997
- Crystal Structure of DMSO Reductase: Redox-Linked Changes in Molybdopterin CoordinationScience, 1996
- Involvement of the narJ and mob gene products in distinct steps in the biosynthesis of the molybdoenzyme nitrate reductase in Escherichia coliMolecular Microbiology, 1996
- Generation of Active [NiFe] Hydrogenase in Vitro from a Nickel-Free Precursor FormBiochemistry, 1996
- Involvement of the narJ or narW gene product in the formation of active nitrate reductase in Escherichia coliMolecular Microbiology, 1992
- Formation of active heterologous nitrate reductases between nitrate reductases A and Z of Escherichia coliMolecular Microbiology, 1992
- Nucleotide sequence of the dmsABC operon encoding the anaerobic dimethylsulphoxide reductase of Escherichia coliMolecular Microbiology, 1988
- Involvement of a protein with molybdenum cofactor in the in vitro activation of nitrate reductase from a chlA mutant of Escherichia coli K12Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1987
- Precursor Forms of the Subunits of Nitrate Reductase inchlAandchlBMutants ofEscherichia coliK12JBIC Journal of Biological Inorganic Chemistry, 1980