Active site of hemerythrin as determined by X-ray absorption fine structure

Journal Article · Tue Sep 20 04:00:00 EDT 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00419a045· OSTI ID:6499942

Zhang, K; Stern, E A; Ellis, F; Sanders-Loehr, J; Shiemke, A K

Extensive X-ray absorption fine structure measurements and analysis have been made on azidomet- and methemerythrin and on the native forms of oxy- and deoxyhemerythrin. Due to the availability of models that have been synthesized to mimic the active site of hemerythrin, it was possible to make a thorough assessment of the various errors in the structural parameters determined by the analysis. It is found that the largest source of error is the lack of complete transferability of amplitude and phase between the standards and hemerythrin. This is of particular importance in distinguishing the contributions of the second-shell low-Z atoms and, thus, has a substantial influence on the determination of the iron-iron distance. The internal consistencies of the various checks and a new formulation of error analysis for the structural parameters give us confidence in the structure determined for the active site. The main result is that as O/sub 2/ is released from oxyhemerythrin, the mu-oxo bridge between the two iron atoms in the active site with an Fe-O distance of 1.8 A converts to a mu-hydroxo bridge in deoxyhemerythrin, expanding the Fe-O distance to 2.0 A. The Fe-Fe distance expands proportionally from 3.24 A in oxyhemerythrin to 3.57 A in deoxyhemerythrin so as to keep the Fe-O-Fe bridging angle approximately constant. These conclusions provide experimental support for the structures of oxy- and deoxyhemerythrin proposed previously on the basis of spectroscopic and preliminary X-ray crystallographic data.

• Research Organization: Univ. of Washington, Seattle (USA)
• OSTI ID: 6499942
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 27:19; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
COHERENT SCATTERING
DATA COVARIANCES
DIFFRACTION
ELEMENTS
IRON
MEMBRANE PROTEINS
METALLOPROTEINS
METALS
MOLECULAR STRUCTURE
NONMETALS
ORGANIC COMPOUNDS
OXYGEN
PROTEINS
RECEPTORS
SCATTERING
TRANSITION ELEMENTS
X-RAY DIFFRACTION