Heme axial methionine fluxionality in Hydrogenobacter thermophilus cytochrome c552

Linghao Zhong, Xin Wen, Terry M. Rabinowitz, Brandy S. Russell, Elizabeth F. Karan, Kara L. Bren

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

The heme group in paramagnetic (S = 1/2) ferricytochromes c typically displays a markedly asymmetric distribution of unpaired electron spin density among the heme pyrrole β substituents. This asymmetry is determined by the orientations of the heme axial ligands, histidine and methionine. One exception to this is ferricytochrome c552 from Hydrogenobacter thermophilus, which has similar amounts of unpaired electron spin density at the β substituents on all four heme pyrroles. Here, determination of the orientation of the magnetic axes and analysis of NMR line shapes for H. thermophilus ferricytochrome c552 is performed. These data reveal that the unusual electronic structure for this protein is a result of fluxionality of the heme axial methionine. It is proposed that the ligand undergoes inversion at the pyramidal sulfur, and the rapid interconversion between two diastereomeric forms results in the unusual heme electronic structure. Thus a fluxional process for a metal-bound amino acid side chain has now been identified.

Original languageEnglish (US)
Pages (from-to)8637-8642
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume101
Issue number23
DOIs
StatePublished - Jun 8 2004

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Heme
Methionine
Pyrroles
Electrons
Ligands
Cytochromes c
Sulfur
Histidine
cytochrome C-552
Metals
Amino Acids
Proteins

All Science Journal Classification (ASJC) codes

  • General

Cite this

Zhong, Linghao ; Wen, Xin ; Rabinowitz, Terry M. ; Russell, Brandy S. ; Karan, Elizabeth F. ; Bren, Kara L. / Heme axial methionine fluxionality in Hydrogenobacter thermophilus cytochrome c552. In: Proceedings of the National Academy of Sciences of the United States of America. 2004 ; Vol. 101, No. 23. pp. 8637-8642.
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Heme axial methionine fluxionality in Hydrogenobacter thermophilus cytochrome c552. / Zhong, Linghao; Wen, Xin; Rabinowitz, Terry M.; Russell, Brandy S.; Karan, Elizabeth F.; Bren, Kara L.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 101, No. 23, 08.06.2004, p. 8637-8642.

Research output: Contribution to journalArticle

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T1 - Heme axial methionine fluxionality in Hydrogenobacter thermophilus cytochrome c552

AU - Zhong, Linghao

AU - Wen, Xin

AU - Rabinowitz, Terry M.

AU - Russell, Brandy S.

AU - Karan, Elizabeth F.

AU - Bren, Kara L.

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AB - The heme group in paramagnetic (S = 1/2) ferricytochromes c typically displays a markedly asymmetric distribution of unpaired electron spin density among the heme pyrrole β substituents. This asymmetry is determined by the orientations of the heme axial ligands, histidine and methionine. One exception to this is ferricytochrome c552 from Hydrogenobacter thermophilus, which has similar amounts of unpaired electron spin density at the β substituents on all four heme pyrroles. Here, determination of the orientation of the magnetic axes and analysis of NMR line shapes for H. thermophilus ferricytochrome c552 is performed. These data reveal that the unusual electronic structure for this protein is a result of fluxionality of the heme axial methionine. It is proposed that the ligand undergoes inversion at the pyramidal sulfur, and the rapid interconversion between two diastereomeric forms results in the unusual heme electronic structure. Thus a fluxional process for a metal-bound amino acid side chain has now been identified.

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