1m1y
From Proteopedia
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'''Chemical Crosslink of Nitrogenase MoFe Protein and Fe Protein''' | '''Chemical Crosslink of Nitrogenase MoFe Protein and Fe Protein''' | ||
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[[Category: Willing, A.]] | [[Category: Willing, A.]] | ||
[[Category: Yoshida, M.]] | [[Category: Yoshida, M.]] | ||
| - | [[Category: | + | [[Category: Chemical crosslink]] |
| - | [[Category: | + | [[Category: Nitrogen fixation]] |
| - | [[Category: | + | [[Category: Nitrogenase]] |
| - | [[Category: | + | [[Category: Protein interaction]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 00:32:08 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 21:32, 2 May 2008
Chemical Crosslink of Nitrogenase MoFe Protein and Fe Protein
Overview
The transient formation of a complex between the component Fe- and MoFe-proteins of nitrogenase represents a central event in the substrate reduction mechanism of this enzyme. Previously, we have isolated an N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide (EDC) cross-linked complex of these proteins stabilized by a covalent isopeptide linkage between Glu 112 and Lys beta400 of the Fe-protein and MoFe-protein, respectively [Willing, A., et al. (1989) J. Biol. Chem. 264, 8499-8503; Willing, A., and Howard, J. B. (1990) J. Biol. Chem. 265, 6596-6599]. We report here the biochemical and structural characterization of the cross-linked complex to assess the mechanistic relevance of this species. Glycinamide inhibits the cross-linking reaction, and is found to be specifically incorporated into Glu 112 of the Fe-protein, without detectable modification of either of the neighboring residues (Glu 110 and Glu 111). This modified protein is still competent for substrate reduction, demonstrating that formation of the cross-linked complex is responsible for the enzymatic inactivation, and not the EDC reaction or the modification of the Fe-protein. Crystallographic analysis of the EDC-cross-linked complex at 3.2 A resolution confirms the site of the isopeptide linkage. The nature of the protein surfaces around the cross-linking site suggests there is a strong electrostatic component to the formation of the complex, although the interface area between the component proteins is small. The binding footprints between proteins in the cross-linked complex are adjacent, but with little overlap, to those observed in the complex of the nitrogenase proteins stabilized by ADP-AlF(4)(-). The results of these studies suggest that EDC cross-linking traps a nucleotide-independent precomplex of the nitrogenase proteins driven by complementary electrostatic interactions that subsequently rearranges in a nucleotide-dependent fashion to the electron transfer competent state observed in the ADP-AlF(4)(-) structure.
About this Structure
1M1Y is a Protein complex structure of sequences from Azotobacter vinelandii. Full crystallographic information is available from OCA.
Reference
Biochemical and structural characterization of the cross-linked complex of nitrogenase: comparison to the ADP-AlF4(-)-stabilized structure., Schmid B, Einsle O, Chiu HJ, Willing A, Yoshida M, Howard JB, Rees DC, Biochemistry. 2002 Dec 31;41(52):15557-65. PMID:12501184 Page seeded by OCA on Sat May 3 00:32:08 2008
