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Peptide-Bound Dinitrosyliron Complexes (DNICs) and Neutral/Reduced-Form Roussin’s Red Esters (RREs/rRREs): Understanding Nitrosylation of [Fe–S] Clusters Leading to the Formation of DNICs and RREs Using a De Novo Design Strategy

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posted on 17.10.2011, 00:00 by Zong-Sian Lin, Feng-Chun Lo, Chih-Hsiang Li, Chih-Hao Chen, Wei-Ning Huang, I-Jui Hsu, Jyh-Fu Lee, Jia-Cherng Horng, Wen-Feng Liaw
This manuscript describes the interaction of low-molecular-weight DNICs with short peptides designed to explore the stability and structure of DNIC–peptide/RRE–peptide constructs. Although characterization of protein-bound and low-molecular-weight DNICs is possible via EPR, XAS, and NRVS, this study demonstrates that the combination of aqueous IR νNO and UV–vis spectra can serve as an efficient tool to characterize and discriminate peptide-bound DNICs and RREs. The de novo chelate-cysteine-containing peptides KC(A)nCK-bound (n = 1–4) dinitrosyliron complexes KC(A)nCK-DNIC (CnA-DNIC) and monodentate-cysteine-containing peptides KCAAK-/KCAAHK-bound Roussin’s red esters (RREs) KCAAK-RRE/KCAAHK-RRE were synthesized and characterized by aqueous IR, UV–vis, EPR, CD, XAS, and ESI-MS. In contrast to the inertness of chelate-cysteine-containing peptide-bound DNICs toward KCAAK/KCAAHK, transformation of KCAAK-RRE/KCAAHK-RRE into CnA-DNIC triggered by CnA and reversible transformation between CnA-DNIC and CnA-RRE via {Fe(NO)2}9-{Fe(NO)2}10 reduced-form peptide-bound RREs demonstrate that the {Fe(NO)2}9 motif displays a preference for chelate-cysteine-containing peptides over monodentate-cysteine-containing peptides. Also, this study may signify that nitrosylation of [Fe–S] proteins generating protein-bound RREs, reduced protein-bound RREs, or protein-bound DNICs are modulated by both the oxidation state of iron and the chelating effect of the bound proteins of [Fe–S] clusters.