1G21

MGATP-BOUND AND NUCLEOTIDE-FREE STRUCTURES OF A NITROGENASE PROTEIN COMPLEX BETWEEN LEU127DEL-FE PROTEIN AND THE MOFE PROTEIN

Summary for 1G21

• Entry DOI: 10.2210/pdb1g21/pdb
• Related: 1G20 1n2c 2min 2nip 3min
• Descriptor: NITROGENASE MOLYBDENUM-IRON PROTEIN ALPHA CHAIN, IRON/SULFUR CLUSTER, NITROGENASE MOLYBDENUM-IRON PROTEIN BETA CHAIN, ... (10 entities in total)
• Functional Keywords: nitrogen-fixation, fe protein, moefe protein, p-cluster, femo cofactor, 4fe-4s, oxidoreductase
• Biological source: Azotobacter vinelandii; More
• Total number of polymer chains: 8
• Total formula weight: 361753.17

Authors

Chiu, H.-J.,Peters, J.W.,Lanzilotta, W.N.,Ryle, M.J.,Seefeldt, L.C.,Howard, J.B.,Rees, D.C. (deposition date: 2000-10-16, release date: 2001-01-31, Last modification date: 2023-08-09)

Primary citation

Chiu, H.,Peters, J.W.,Lanzilotta, W.N.,Ryle, M.J.,Seefeldt, L.C.,Howard, J.B.,Rees, D.C.
MgATP-Bound and nucleotide-free structures of a nitrogenase protein complex between the Leu 127 Delta-Fe-protein and the MoFe-protein.
Biochemistry, 40:641-650, 2001

PubMed Abstract: 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.

PubMed: 11170380
DOI: 10.1021/bi001645e

Experimental method

X-RAY DIFFRACTION (3 Å)