The binding of molybdate to uteroferrin. Hyperfine interactions of the binuclear center with 95Mo, 1H, and 2H.

A New Microbial Pathway for Organophosphonate Degradation Catalyzed by Two Previously Misannotated Non-Heme-Iron Oxygenases

“…In the absence of substrate (Figure , black), the sample exhibited a broad axial signal with apparent principal g values of <2 ([1.94, 1.78, 1.78]). This spectrum is similar to those of antiferromagnetically coupled ( S total = 1 / 2 ) Fe 2 (II/III) clusters in other proteins. ,, Comparison of the integrated intensity of this signal to that of a spin concentration Cu­(II)-EDTA standard indicated the presence of ∼0.3 spin/iron cluster or ∼0.6 spin/diiron cluster, similar to the quantity deduced in the Mössbauer analysis of the parallel sample. The signal became markedly more rhombic ( g = [1.94, 1.82, 1.65]) upon addition of ( R )-OH-TMAEP (Figure , red), suggestive of substrate binding to the cofactor, as also seen in MIOX and PhnZ. , Addition of the unmethylated analogue, ( R )-OH-AEP (the PhnZ substrate), also perturbed the EPR spectrum but gave a broader, more complex signal (Figure , blue).…”

“…This spectrum is similar to those of antiferromagnetically coupled (S total = 1 / 2 ) Fe 2 (II/III) clusters in other proteins. 21,79,80 Comparison of the integrated intensity of this signal to that of a spin concentration Cu(II)-EDTA standard indicated the presence of ∼0.3 spin/iron cluster or ∼0.6 spin/diiron cluster, similar to the quantity deduced in the Mossbauer analysis of the parallel sample. The signal became markedly more rhombic (g = [1.94, 1.82, 1.65]) upon addition of (R)-OH-TMAEP (Figure 9, red), suggestive of substrate binding to the cofactor, as also seen in MIOX and PhnZ.…”

Multiple binding sites for tetrahedral oxyanion inhibitors of bovine spleen purple acid phosphatase

“…The kinetics results provide a basis for interpretation of previous spectroscopic studies of the interaction of tetrahedral oxyanions with the binuclear iron center of PAP's. ENDOR studies on the PAP from porcine uterine fluid in the presence of Mo04 indicate that Mo04 binds to the dinuclear iron center (Doi et al, 1988a), while recent direct EPR studies have shown that P04 binds directly to the ferric iron in the FeZn form of the porcine enzyme (and by implication to the diiron center of the native enzyme) (David & Que, 1990). According to Scheme I and Figure 4, the Mo04 results reflect binding of the oxyanion to a site that is distinct from the substrate binding site.…”

Binuclear Metallohydrolases

“…Magnetic susceptibility, EPR, and NMR measurements have indicated a strong antiferromagnetic interaction in the oxidized enzyme (−2 J > 80 cm -1 ) ,,,, but a weaker antiferromagnetic coupling in the reduced enzyme (2 J = −11 to −22 cm -1 ). − 1 H NMR data have been particularly informative about the ligands, initially indicating His coordination and identifying Tyr as a Fe(III) ligand in the reduced enzyme . NMR measurements later provided evidence for Nε coordination of His to the Fe(III) and Nδ coordination of Histo the Fe(II) in the reduced enzyme and for carboxylate coordination to the metal ions. − Advanced EPR techniques, including ENDOR, ESEEM, , and LEFE, have confirmed His ligation and a trapped valence description of the Fe(III)Fe(II) site in the reduced enzyme and have demonstrated solvent accessibility and probable coordination to the metal ions. X-ray absorption and EXAFS measurements − ruled out sulfur ligation, indicated metal−ligand bond lengths, provided metal−metal distances in the reduced (3.5 Å) 111 and oxidized (3.0 Å; 3.2−3.3 Å 111 ) forms, and suggested bridging ligand coordination.…”