Mechanistic significance of the preparatory migration of hydrogen atoms around the FeMo-co active site of nitrogenase
- PMID: 16700544
- DOI: 10.1021/bi052217h
Mechanistic significance of the preparatory migration of hydrogen atoms around the FeMo-co active site of nitrogenase
Abstract
The migration of H atoms over S and Fe atoms in the reaction domain of FeMo-co, the active site of nitrogenase, is described and used to explain mechanistic data on the catalyzed reductions of N(2) and C(2)H(2). After electron transfer to FeMo-co, H atoms are generated by fast proton supply to S3B (atom labels from structure 1M1N) and migrate vectorially via several pathways from S3B to locations on the FeMo-co face, specifically Fe6, S2B, Fe2, and S2A (calculated reaction profiles are reported). The E(n)H(n) reduction levels (n = 1-4) in the Thorneley-Lowe kinetic-mechanistic schemes are each potential sequences of substructures with different distributions of H atoms. The positions of H atoms influence the binding of substrates N(2) and C(2)H(2), and the bound substrate subsequently blocks further migration of H atoms past the binding site. This model provides a consistent structural interpretation of (a) the two-site reactivity of C(2)H(2) and the differentiation of the high- and low-affinity sites as due to different preparatory H migration; (b) the differing mutual inhibitions of N(2) and C(2)H(2) in wild-type protein; (c) the modified reactivity of the Azotobacter vinelandii alpha-(Gly)69(Ser) mutant with N(2) and C(2)H(2); and (d) the basis for the stereoselectivity of hydrogenation of C(2)D(2) and its loss in some mutant proteins. Some structures for initially bound N(2) and C(2)H(2), and their hydrogenated intermediates, are presented. The key new concept is that binding sites and binding states for substrates and intermediates are characterized not only by their locations on the FeMo-co face but also by the structural and temporal status of the distribution of H atoms over the FeMo-co reaction domain.
Similar articles
-
The hydrogen chemistry of the FeMo-co active site of nitrogenase.J Am Chem Soc. 2005 Aug 10;127(31):10925-42. doi: 10.1021/ja0504946. J Am Chem Soc. 2005. PMID: 16076199
-
The mechanistically significant coordination chemistry of dinitrogen at FeMo-co, the catalytic site of nitrogenase.J Am Chem Soc. 2007 Feb 7;129(5):1076-88. doi: 10.1021/ja0644428. J Am Chem Soc. 2007. PMID: 17263388
-
The chemical mechanism of nitrogenase: calculated details of the intramolecular mechanism for hydrogenation of eta(2)-N(2) on FeMo-co to NH(3).Dalton Trans. 2008 Nov 21;(43):5977-91. doi: 10.1039/b806100a. Epub 2008 Sep 24. Dalton Trans. 2008. PMID: 19082054
-
Substrate interactions with nitrogenase: Fe versus Mo.Biochemistry. 2004 Feb 17;43(6):1401-9. doi: 10.1021/bi036038g. Biochemistry. 2004. PMID: 14769015 Review.
-
Elucidating the coordination chemistry and mechanism of biological nitrogen fixation.Chem Asian J. 2007 Aug 3;2(8):936-46. doi: 10.1002/asia.200700131. Chem Asian J. 2007. PMID: 17614310 Review.
Cited by
-
Synthesis, Characterization, and Nitrogenase-Relevant Reactions of an Iron Sulfide Complex with a Bridging Hydride.J Am Chem Soc. 2015 Oct 21;137(41):13220-3. doi: 10.1021/jacs.5b06841. Epub 2015 Oct 12. J Am Chem Soc. 2015. PMID: 26457740 Free PMC article.
-
Reaction Mechanism for CO Reduction by Mo-Nitrogenase Studied by QM/MM.Inorg Chem. 2024 Aug 26;63(34):15951-15963. doi: 10.1021/acs.inorgchem.4c02323. Epub 2024 Aug 14. Inorg Chem. 2024. PMID: 39141025 Free PMC article.
-
Investigating the Molybdenum Nitrogenase Mechanistic Cycle Using Spectroelectrochemistry.J Am Chem Soc. 2025 Jan 15;147(2):2099-2114. doi: 10.1021/jacs.4c16047. Epub 2025 Jan 2. J Am Chem Soc. 2025. PMID: 39746667 Free PMC article.
-
The Mechanism of N-N Double Bond Cleavage by an Iron(II) Hydride Complex.J Am Chem Soc. 2016 Sep 21;138(37):12112-23. doi: 10.1021/jacs.6b04654. Epub 2016 Sep 6. J Am Chem Soc. 2016. PMID: 27598037 Free PMC article.
-
A molecular pathway for the egress of ammonia produced by nitrogenase.Sci Rep. 2013 Nov 18;3:3237. doi: 10.1038/srep03237. Sci Rep. 2013. PMID: 24241241 Free PMC article.
Publication types
MeSH terms
Substances
LinkOut - more resources
Full Text Sources
Miscellaneous