X-ray absorption spectral study of ferric high-spin hemoproteins: XANES evidences for coordination structure of the heme iron

1990 ◽  
Vol 112 (8) ◽  
pp. 2921-2924 ◽  
Author(s):  
Yoshitsugu Shiro ◽  
Fumitoshi Sato ◽  
Tomohiko Suzuki ◽  
Tetsutaro Iizuka ◽  
Tadashi Matsushita ◽  
...  
Keyword(s):  
High Spin ◽  
Spectral Study ◽  
Heme Iron ◽  
Coordination Structure ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Oxygen Binding and Redox Properties of the Heme in Soluble Guanylate Cyclase

2011 ◽  
Vol 286 (18) ◽  
pp. 15678-15687 ◽  
Author(s):  
Ryu Makino ◽  
Sam-yon Park ◽  
Eiji Obayashi ◽  
Tetsutaro Iizuka ◽  
Hiroshi Hori ◽  
...  
Keyword(s):  
High Spin ◽  
Guanylate Cyclase ◽  
Soluble Guanylate Cyclase ◽  
Heme Iron ◽  
Redox Properties ◽  
Oxygen Binding ◽  
X Ray ◽  
Midpoint Potential ◽  
Ferrous Heme ◽  
X Ray Absorption

Soluble guanylate cyclase is an NO-sensing hemoprotein that serves as a NO receptor in NO-mediated signaling pathways. It has been believed that this enzyme displays no measurable affinity for O2, thereby enabling the selective NO sensing in aerobic environments. Despite the physiological significance, the reactivity of the enzyme-heme for O2 has not been examined in detail. In this paper we demonstrated that the high spin heme of the ferrous enzyme converted to a low spin oxyheme (Fe2+-O2) when frozen at 77 K in the presence of O2. The ligation of O2 was confirmed by EPR analyses using cobalt-substituted enzyme. The oxy form was produced also under solution conditions at −7 °C, with the extremely low affinity for O2. The low O2 affinity was not caused by a distal steric protein effect and by rupture of the Fe2+-proximal His bond as revealed by extended x-ray absorption fine structure. The midpoint potential of the enzyme-heme was +187 mV, which is the most positive among high spin protoheme-hemoproteins. This observation implies that the electron density of the ferrous heme iron is relatively low by comparison to those of other hemoproteins, presumably due to the weak Fe2+-proximal His bond. Based on our results, we propose that the weak Fe2+-proximal His bond is a key determinant for the low O2 affinity of the heme moiety of soluble guanylate cyclase.

scholarly journals L-edge X-ray Absorption Spectroscopy of Non-Heme Iron Sites:  Experimental Determination of Differential Orbital Covalency

2003 ◽  
Vol 125 (42) ◽  
pp. 12894-12906 ◽  
Author(s):  
Erik C. Wasinger ◽  
Frank M. F. de Groot ◽  
Britt Hedman ◽  
Keith O. Hodgson ◽  
Edward I. Solomon
Keyword(s):  
Experimental Determination ◽  
Absorption Spectroscopy ◽  
Heme Iron ◽  
X Ray ◽  
Non Heme Iron ◽  
X Ray Absorption

scholarly journals Fingerprinting Electronic Structure of Heme Iron by Ab Initio Modeling of Metal L-Edge X-ray Absorption Spectra

2018 ◽  
Vol 15 (1) ◽  
pp. 477-489 ◽  
Author(s):  
Meiyuan Guo ◽  
Erik Källman ◽  
Rahul V. Pinjari ◽  
Rafael C. Couto ◽  
Lasse Kragh Sørensen ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Absorption Spectra ◽  
Heme Iron ◽  
X Ray ◽  
Ab Initio Modeling ◽  
X Ray Absorption

X-ray-absorption spectral study of theR2Fe17−xMxsolid solutions (R=Ce, Nd andM=Al, Si)

1997 ◽  
Vol 56 (10) ◽  
pp. 6100-6106 ◽  
Author(s):  
D. Vandormael ◽  
F. Grandjean ◽  
V. Briois ◽  
D. P. Middleton ◽  
K. H. J. Buschow ◽  
...  
Keyword(s):  
Spectral Study ◽  
X Ray ◽  
X Ray Absorption

The K edges of the heme iron in the x-ray absorption spectra of native and carboxymethylated cytochrome c

1981 ◽  
Vol 15 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Alfredo Colosimo ◽  
Maurizio Brunori ◽  
Francesco Andreasi ◽  
Settimio Mobilio
Keyword(s):  
Cytochrome C ◽  
Absorption Spectra ◽  
Heme Iron ◽  
X Ray ◽  
X Ray Absorption
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