13C NMR Spectroscopy of Core Heme Carbons as a Simple Tool to Elucidate the Coordination State of Ferric High-Spin Heme Proteins

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• 作者：Aileen Y. Alontaga ; Richard A. Bunce ; Angela Wilks ; Mario Rivera
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：October 30, 2006
• 年：2006
• 卷：45
• 期：22
• 页码：8876 - 8881
• 全文大小：157K
• 年卷期：v.45,no.22(October 30, 2006)
• ISSN：1520-510X

文摘

Evidence is presented demonstrating that the magnitudes of the ¹³C chemical shifts originating from heme mesocarbons provide a straightforward diagnostic tool to elucidate the coordination state of high-spin heme proteins andenzymes. Pentacoordinate high-spin heme centers exhibit ¹³C meso shifts centered at approximately 250 ppm,whereas their hexacoordinate counterparts exhibit ¹³C shifts centered at approximately -80 ppm. The relativelysmall spectral window (400 to -100 ppm) covering the meso-¹³C shifts, the relatively narrow lines of these resonances,and the availability of biosynthetic methods to prepare ¹³C-labeled heme (Rivera, M.; Walker, F. A. Anal. Biochem.1995, 230, 295-302) make this approach practical. The theoretical basis for the distinct chemical shifts observedfor meso carbons from hexacoordinate high-spin hemes relative to their pentacoordinate counterparts are now wellunderstood (Cheng, R.-J.; Chen, P. Y.; Lovell, T.; Liu, T.; Noodleman, L.; Case, D. A. J. Am. Chem. Soc. 2003,125, 6774-6783), which indicates that the magnitude of the meso-carbon chemical shifts can be used as a simpleand reliable diagnostic tool for determining the coordination state of the heme active sites, independent of thenature of the proximal ligand. Proof of the principle for the ¹³C NMR spectroscopic approach is demonstrated usinghexa- and pentacoordinate myoglobin. Subsequently, ¹³C NMR spectroscopy has been used to unambiguouslydetermine that a recently discovered heme protein from Shigella dysenteriae (ShuT) is pentacoordinate.