title: Computational Insights into Five- versus Six-Coordinate Iron Center in Ferrous Soybean Lipoxygenase.
abstract: Soybean lipoxygenase (SLO) serves as a prototype for fundamental understanding of hydrogen tunneling in enzymes. Its reactivity depends on the active site structure around a mononuclear, nonheme iron center. The available crystal structures indicate five-coordinate iron, while magnetic circular dichroism experiments suggest significant populations of both five-coordinate (5C) and six-coordinate (6C) iron in ferrous SLO. Quantum mechanical calculations of gas phase models produce only 6C geometries. Herein mixed quantum mechanical/molecular mechanical (QM/MM) calculations are employed to identify and characterize the 5C and 6C geometries. These calculations highlight the importance of the protein environment, particularly two Gln residues in a hydrogen-bonding network with Asn694, the ligand that can dissociate. This hydrogen-bonding network is similar in both geometries, but twisting of a dihedral angle in Asn694 moves its oxygen away from the iron in the 5C geometry. These insights are important for future simulations of SLO.
authors.affiliation: Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Tao
authors.initials: T
authors.lastname: Yu
authors.affiliation: Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Soudackov
authors.affiliation: Department of Chemistry, 600 South Mathews Avenue, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Sharon
authors.initials: S
authors.lastname: Hammes-Schiffer
mesh_terms: D007501:Iron / Q000737:chemistry*; D008084:Lipoxygenase / Q000737:chemistry*; D008958:Models, Molecular; D013025:Glycine max / Q000737:chemistry*
chemical_list: D007501:Iron; D008084:Lipoxygenase