2C8V: Insights Into The Role Of Nucleotide-dependent Conformational Change In Nitrogenase Catalysis: Structural Characterization Of The Nitrogenase Fe Protein Leu127 Deletion Variant With Bound Mgatp

Citation:
Abstract
In the present work, determination of the structure of the nitrogenase Leu 127 deletion variant Fe protein with MgATP bound is presented, along with density functional theory calculations, to provide insights into the roles of MgATP in the nitrogenase reaction mechanism. Comparison of the MgATP-bound structure of this Fe protein to the nucleotide-free form indicates that the binding of MgATP does not alter the overall structure of the variant significantly with only small differences in the conformation of amino acids in direct contact with the two bound MgATP molecules being seen. The earlier observation of splitting of the [4Fe-4S] cluster into two [2Fe-2S] clusters was observed to be unaltered upon binding MgATP. Density functional theory was used to probe the assignment of ligands to the two [2Fe-2S] rhombs. The Mg(2+) environment in the MgATP-bound structure of the Leu127 deletion Fe protein is similar to that observed for the Fe protein in the nitrogenase Fe protein: MoFe protein complex stabilized by MgADP and tetrafluoroaluminate suggesting that large scale conformational change implicated for the Fe protein may not be mediated by changes in the Mg(2+) coordination. The results presented here indicated that MgATP may enhance the stability of an open conformation and prohibit intersubunit interactions, which have been implicated in promoting nucleotide hydrolysis. This could be critical to the tight control of MgATP hydrolysis observed within the nitrogenase complex and may be important for maintaining unidirectional electron flow toward substrate reduction.
PDB ID: 2C8VDownload
MMDB ID: 39096
PDB Deposition Date: 2005/12/8
Updated in MMDB: 2006/11
Experimental Method:
x-ray diffraction
Resolution: 2.5  Å
Source Organism:
Similar Structures:
Biological Unit for 2C8V: monomeric; determined by author and by software (PQS)
Molecular Components in 2C8V
Label Count Molecule
Protein (1 molecule)
1
Nitrogenase Iron Protein 1
Molecule annotation
Chemicals (4 molecules)
1
2
2
1
3
1
* Click molecule labels to explore molecular sequence information.

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