An extended-X-ray-absorption-fine-structure study of freeze-dried and solution ovotransferrin. Evidence for water co-ordination at the metal-binding sites.
Our previous extended-X-ray-absorption-fine-structure (e.x.a.f.s.) study has shown that the probable iron environment in chicken ovotransferrin involves two low-Z ligands (consistent with phenolate linkages) at 0.185(1) nm and four low-Z ligands at 0.204(1) nm [Garratt, Evans, Hasnain & Lindley (1986) Biochem. J. 233, 479-484]. Herein we provide additional information from the e.x.a.f.s. and near-edge structure suggestive of a decrease in the co-ordination number of ovotransferrin-bound iron upon freeze-drying. These effects are reversible, and exposure of the freeze-dried material to a humid atmosphere results in reversion to the solution spectra. Progressive rehydration was monitored by using e.p.r. spectroscopy and was confirmed by recording the high-resolution X-ray-absorption near-edge structure (x.a.n.e.s.). The results suggest the presence of a labile water molecule at the iron-binding sites of ovotransferrin in solution.
Hasnain
S S
SS
S.E.R.C. Daresbury Laboratory, Warrington, U.K.
Evans
R W
RW
Garratt
R C
RC
Lindley
P F
PF
D000818:Animals; D001665:Binding Sites; D002645:Chickens; D003207:Conalbumin; D004527:Egg Proteins; D004578:Electron Spin Resonance Spectroscopy; D005612:Freeze Drying; D007501:Iron / Q000032:analysis; D012996:Solutions; D013057:Spectrum Analysis; D014867:Water; D014965:X-Rays
D004527:Egg Proteins; D012996:Solutions; D014867:Water; D003207:Conalbumin; D007501:Iron