Solution and structural characterization of iron(II) complexes with ortho-halogenated phenolates: insights into potential substrate binding modes in hydroquinone dioxygenases.
The new ligand cis,cis-1,3,5-tris-(E)-(tolylideneimino)cyclohexane (TACH-o-tolyl) forms a 1:1 complex with iron(II). Addition of substituted phenolates forms 1:1:1 ligand:iron:phenolate complexes, which have been characterized both in the solid state and in solution. There is complete binding of the phenolate to the complex only when there are ortho-halogens on the phenolate. The tertiary complexes with ortho-halo-substituted phenolates exhibit short Fe-halogen distances, and the complex containing a non-coordinating but similarly sized ortho-methyl phenolate has a significantly different conformation and coordination geometry. Therefore, it is likely that the metal-halogen interaction stabilizes the complexes. The iron(II)-halogen interaction in these complexes may explain the substrate specificity of PcpA and LinE, enzymes that preferentially bind phenols and hydroquinones containing halogen substituents in ortho positions.
Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.
Sara S
SS
Rocks
William W
WW
Brennessel
Timothy E
TE
Machonkin
Patrick L
PL
Holland
D001419:Bacteria / Q000201:enzymology*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000737:chemistry*; D054879:Halogenation; D006873:Hydroquinones / Q000737:chemistry*; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D013379:Substrate Specificity
D005296:Ferrous Compounds; D006873:Hydroquinones; D010636:Phenols; D010088:Oxidoreductases; C023314:hydroquinone dehydrogenases