Electronic Structure of the Ground and Excited States of the CuA Site by NMR Spectroscopy

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• 作者：Luciano A. Abriata ; Gabriela N. Ledesma ; Roberta Pierattelli ; Alejandro J. Vila
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：February 11, 2009
• 年：2009
• 卷：131
• 期：5
• 页码：1939-1946
• 全文大小：220K
• 年卷期：v.131,no.5(February 11, 2009)
• ISSN：1520-5126

文摘

The electronic properties of Thermus thermophilus Cu_A in the oxidized form were studied by ¹H and ¹³C NMR spectroscopy. All of the ¹H and ¹³C resonances from cysteine and imidazole ligands were observed and assigned in a sequence-specific fashion. The detection of net electron spin density on a peptide moiety is attributed to the presence of a H-bond to a coordinating sulfur atom. This hydrogen bond is conserved in all natural Cu_A variants and plays an important role for maintaining the electronic structure of the metal site, rendering the two Cys ligands nonequivalent. The anomalous temperature dependence of the chemical shifts is explained by the presence of a low-lying excited state located about 600 cm⁻¹ above the ground state. The room-temperature shifts can be described as the thermal average of a σ_u* ground state and a π_u excited state. These results provide a detailed description of the electronic structure of the Cu_A site at atomic resolution in solution at physiologically relevant temperature.