1g20
MGATP-BOUND AND NUCLEOTIDE-FREE STRUCTURES OF A NITROGENASE PROTEIN COMPLEX BETWEEN LEU127DEL-FE PROTEIN AND THE MOFE PROTEIN
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OverviewOverview
A mutant form of the nitrogenase iron protein with a deletion of residue, Leu 127, located in the switch II region of the nucleotide binding site, forms a tight, inactive complex with the nitrogenase molybdenum iron, (MoFe) protein in the absence of nucleotide. The structure of this complex, generated with proteins from Azotobacter vinelandii (designated the, L127Delta-Av2-Av1 complex) has been crystallographically determined in the, absence of nucleotide at 2.2 A resolution and with bound MgATP (introduced, by soaking) at 3.0 A resolution. As observed in the structure of the, complex between the wild-type A. vinelandii nitrogenase proteins, stabilized with ADP.AlF(4-), the most significant conformational changes, in the L127Delta complex occur in the Fe-protein component. While the, interactions at the interface between the MoFe-protein and Fe-proteins are, conserved in the two complexes, significant differences are evident at the, subunit-subunit interface of the dimeric Fe-proteins, with the, L127Delta-Av2 structure having a more open conformation than the wild-type, Av2 in the complex stabilized by ADP.AlF(4-). Addition of MgATP to the, L127Delta-Av2-Av1 complex results in a further increase in the separation, between Fe-protein subunits so that the structure more closely resembles, that of the wild-type, nucleotide-free, uncomplexed Fe-protein, rather, than the Fe-protein conformation in the ADP.AlF(4-) complex. The L127Delta, mutation precludes key interactions between the Fe-protein and nucleotide, especially, but not exclusively, in the region corresponding to the switch, II region of G-proteins, where the deletion constrains Gly 128 and Asp 129, from forming hydrogen bonds to the gamma-phosphate and activating water, for attack on this group, respectively. These alterations account for the, inability of this mutant to support mechanistically productive ATP, hydrolysis. The ability of the L127Delta-Av2-Av1 complex to bind MgATP, demonstrates that dissociation of the nitrogenase complex is not required, for nucleotide binding.
About this StructureAbout this Structure
1G20 is a Protein complex structure of sequences from Azotobacter vinelandii with CA, SF4, HCA, CFM and CLF as ligands. Active as Nitrogenase, with EC number 1.18.6.1 Full crystallographic information is available from OCA.
ReferenceReference
MgATP-Bound and nucleotide-free structures of a nitrogenase protein complex between the Leu 127 Delta-Fe-protein and the MoFe-protein., Chiu H, Peters JW, Lanzilotta WN, Ryle MJ, Seefeldt LC, Howard JB, Rees DC, Biochemistry. 2001 Jan 23;40(3):641-50. PMID:11170380
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