An Unexpected P-Cluster like Intermediate En Route to the Nitrogenase FeMo-co

Chemical Science ◽

10.1039/d1sc00289a ◽

2021 ◽

Author(s):

Leon P. Jenner ◽

Mickaël V Cherrier ◽

Patricia Amara ◽

Luis M Rubio ◽

Yvain Nicolet

Keyword(s):

Molybdenum Cofactor ◽

Mofe Protein ◽

Iron Molybdenum Cofactor

The nitrogenase MoFe protein contains two different FeS centers, the P-cluster and the iron-molybdenum cofactor (FeMo-co). The former is a [Fe8S7] center responsible for conveying electrons to the latter, a...

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Nitrogenase from nifV mutants of Klebsiella pneumoniae contains an altered form of the iron-molybdenum cofactor

Biochemical Journal ◽

10.1042/bj2170317 ◽

1984 ◽

Vol 217 (1) ◽

pp. 317-321 ◽

Cited By ~ 110

Author(s):

T R Hawkes ◽

P A McLean ◽

B E Smith

Keyword(s):

Klebsiella Pneumoniae ◽

Active Site ◽

Molybdenum Cofactor ◽

Wild Type ◽

H2 Evolution ◽

Mofe Protein ◽

Fe Protein ◽

Metal Contents ◽

Altered Form ◽

Iron Molybdenum Cofactor

When the iron-molybdenum cofactor (FeMoco) was extracted from the MoFe protein of nitrogenase from a nifV mutant of Klebsiella pneumoniae and combined with the FeMoco-deficient MoFe protein from a nifB mutant, the resultant MoFe protein exhibited the NifV phenotype, i.e. in combination with wild-type Fe protein it exhibited poor N2-fixation activity and its H2-evolution activity was inhibited by CO. These data provide strong evidence that FeMoco contains the active site of nitrogenase. The metal contents and e.p.r. properties of FeMoco from wild-type and nifV mutants of K. pneumoniae are very similar.

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Low-temperature magnetic-circular-dichroism spectroscopy of the iron-molybdenum cofactor and the complementary cofactor-less MoFe protein of Klebsiella pneumoniae nitrogenase

Biochemical Journal ◽

10.1042/bj2190495 ◽

1984 ◽

Vol 219 (2) ◽

pp. 495-503 ◽

Cited By ~ 15

Author(s):

A E Robinson ◽

A J M Richards ◽

A J Thomson ◽

T R Hawkes ◽

B E Smith

Keyword(s):

Low Temperature ◽

Klebsiella Pneumoniae ◽

Magnetic Circular Dichroism ◽

Molybdenum Cofactor ◽

Magnetization Curves ◽

Mofe Protein ◽

Paramagnetic Component ◽

Magnetic Circular Dichroism Spectroscopy ◽

Iron Molybdenum Cofactor ◽

Circular Dichroïsm

The major metal clusters of the MoFe protein, Kpl, of Klebsiella pneumoniae nitrogenase were characterized separately by low-temperature magnetic-circular-dichroism spectroscopy. The spectra and magnetization curves of the extracted iron-molybdenum cofactor, FeMoco, and of ‘P’ clusters in NifB - Kpl, the inactive, FeMoco -less, MoFo protein from an nifB mutant, were measured and compared with those of the holoprotein. (When FeMoco and NifB - Kpl are combined, active Kpl is formed.) Reduced NifB - Kpl had a spectrum with a weak, paramagnetic, component superimposed on a diamagnetic background. The paramagnetic component was assigned to a contaminating, e.p.r.-active, species. Thionine-oxidized NifB - Kpl had a spectrum and magnetization properties very similar to those of thionine-oxidized Kpl, demonstrating that the ‘P’ clusters are not significantly affected by the absence of the FeMoco clusters. The spectra of reduced isolated FeMoco had similar magnetization curves but sharper features and higher intensities than those of this centre in dithionite-reduced Kpl . Furthermore, a shoulder near 580 nm in the Kpl spectrum was absent from that of FeMoco . This may be due to the loss of a ligand or to a change in symmetry of the FeMoco cluster on extraction.

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