Nitrogenase: Difference between revisions
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N<sub>2</sub> + 8 H<sup>+</sup> + 16 MgATP + 8 e<sup>-</sup> → 2NH<sub>3</sub> + H<sub>2</sub> + 16 MgADP + 16 P<sub>i</sub> | N<sub>2</sub> + 8 H<sup>+</sup> + 16 MgATP + 8 e<sup>-</sup> → 2NH<sub>3</sub> + H<sub>2</sub> + 16 MgADP + 16 P<sub>i</sub> | ||
Two different proteins comprise the nitrogenase complex. The FeMo protein binds substrate and reduces H<sup>+</sup> and N<sub>2</sub> to H<sub>2</sub> and ammonia, while the Fe protein receives electrons from ferredoxin, hydrolyzes ATP, and reduces the FeMo protein. To the right is shown a crystal structure (PDB entry [[1n2c]]) where two complexes of FeMo protein bound to Fe protein were crystallized together. Click here to see only <scene name='Sandbox_10/1n2c_single_complex/ | Two different proteins comprise the nitrogenase complex. The FeMo protein binds substrate and reduces H<sup>+</sup> and N<sub>2</sub> to H<sub>2</sub> and ammonia, while the Fe protein receives electrons from ferredoxin, hydrolyzes ATP, and reduces the FeMo protein. To the right is shown a crystal structure (PDB entry [[1n2c]]) where two complexes of FeMo protein bound to Fe protein were crystallized together. Click here to see only <scene name='Sandbox_10/1n2c_single_complex/2'>one complex</scene>. | ||
The <scene name='Sandbox_10/1n2c_fe_protein/1'>Fe protein</scene> is here bound to two <scene name='Sandbox_10/1n2c_atp/3'>ADP x AlF<sub>4</sub><sup>-</sup></scene>, an analog for the planar transition state of ATP hydrolysis. The motif that binds ATP is a conserved nucleotide binding motif called Walker's motif A. Coloring by <scene name='Sandbox_10/1n2c_atp_evolutionary/1'>evolutionary conservation</scene>, the nucleotide binding pocket is clear. | The <scene name='Sandbox_10/1n2c_fe_protein/1'>Fe protein</scene> is here bound to two <scene name='Sandbox_10/1n2c_atp/3'>ADP x AlF<sub>4</sub><sup>-</sup></scene>, an analog for the planar transition state of ATP hydrolysis. The motif that binds ATP is a conserved nucleotide binding motif called Walker's motif A. Coloring by <scene name='Sandbox_10/1n2c_atp_evolutionary/1'>evolutionary conservation</scene>, the nucleotide binding pocket is clear. | ||
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At the bottom of the protein, where the Fe protein comes into contact with the FeMo protein, is a 4Fe:4S cluster, held in place by <scene name='Sandbox_10/1n2c_fes_cluster_cys/1'>cysteines</scene>. This cluster accepts electrons from ferredoxin and gives electrons to the FeMo protein. | At the bottom of the protein, where the Fe protein comes into contact with the FeMo protein, is a 4Fe:4S cluster, held in place by <scene name='Sandbox_10/1n2c_fes_cluster_cys/1'>cysteines</scene>. This cluster accepts electrons from ferredoxin and gives electrons to the FeMo protein. | ||
When the Fe protein is bound to the FeMo protein <scene name='Sandbox_10/1n2c_single_complex/ | When the Fe protein is bound to the FeMo protein <scene name='Sandbox_10/1n2c_single_complex/2'>(zoom out)</scene>, ATP is hydrolyzed and electrons that were transferred to the 4Fe:4S cluster of the Fe protein by ferredoxin are transferred to the FeMo protein. The crystal structure of the complete nitrogenase complex reveals how the binding of the Fe and FeMo proteins, the hydrolysis of ATP, and the transfer of electrons are all coupled. | ||
Compared to the crystal structure of Fe protein that is not bound to FeMo protein, Fe protein complexed with FeMo protein | Compared to the crystal structure of Fe protein that is not bound to FeMo protein, Fe protein complexed with FeMo protein | ||