Universität zu Köln

Klein, Eric L., Belaidi, Abdel Ali, Raitsimring, Arnold M., Davis, Amanda C., Kraemer, Tobias ORCID: 0000-0001-5842-9553, Astashkin, Andrei V., Neese, Frank ORCID: 0000-0003-4691-0547, Schwarz, Guenter ORCID: 0000-0002-2118-9338 and Enemark, John H. (2014). Pulsed Electron Paramagnetic Resonance Spectroscopy of S-33-Labeled Molybdenum Cofactor in Catalytically Active Bioengineered Sulfite Oxidase. Inorg. Chem., 53 (2). S. 961 - 972. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-510X

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Abstract

Molybdenum enzymes contain at. least one pyranopterin dithiolate (molybdopterin, MPT) moiety that coordinates Mo through two dithiolate (dithiolene) sulfur atoms. For sulfite oxidase (SO), hyperfine interactions (hfi) and nuclear quadrupole interactions (nqi) of magnetic nuclei (I not equal 0) near the Mo(V) (d(1)) center have been measured using high-resolution pulsed electron paramagnetic resonance (EPR) methods and interpreted with the help of density functional theory (DFT) calculations. These have provided important insights about the active site structure and the reaction mechanism of the enzyme. However, it has not been possible to use EPR to probe the dithiolene sulfurs directly since naturally abundant S-32 has no nuclear spin (I = 0). Here we describe direct incorporation of S-33 (I = 3/2), the only stable magnetic sulfur isotope, into MPT using controlled in vitro synthesis with purified proteins. The electron spin echo envelope modulation (ESEEM) spectra from S-33-labeled MPT in this catalytically active SO variant are dominated by the interdoublet transition arising from the strong nuclear quadrupole interaction, as also occurs for the S-33-labeled exchangeable equatorial sulfite ligand [Klein, E. L., et al. Inorg. Chem. 2012, 51, 14081418]. The estimated experimental hfi and nqi parameters for S-33 (a(iso) = 3 MHz and e(2)Qq/h = 25 MHz) are in good agreement with those predicted by DFT. In addition, the DFT calculations show that the two S-33 atoms are indistinguishable by EPR and reveal a strong intermixing between their out-of-plane p(z) orbitals and the d(xy) orbital of Mo(V).

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Klein, Eric L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Belaidi, Abdel Ali UNSPECIFIED UNSPECIFIED UNSPECIFIED Raitsimring, Arnold M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Davis, Amanda C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kraemer, Tobias UNSPECIFIED orcid.org/0000-0001-5842-9553 UNSPECIFIED Astashkin, Andrei V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Neese, Frank UNSPECIFIED orcid.org/0000-0003-4691-0547 UNSPECIFIED Schwarz, Guenter UNSPECIFIED orcid.org/0000-0002-2118-9338 UNSPECIFIED Enemark, John H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-448412
DOI:	10.1021/ic4023954
Journal or Publication Title:	Inorg. Chem.
Volume:	53
Number:	2
Page Range:	S. 961 - 972
Date:	2014
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-510X
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Biochemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RAY-ABSORPTION SPECTROSCOPY; DENSITY-FUNCTIONAL CALCULATIONS; MAGNETIC CIRCULAR-DICHROISM; PLANAR METAL COMPLEXES; GAUSSIAN-BASIS SETS; LIGAND K-EDGE; CORRELATION-ENERGY; EPR SPECTROSCOPY; ATOMS LI; PH FORM Multiple languages Chemistry, Inorganic & Nuclear Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/44841