Gn. George et al., DIRECT OBSERVATION OF BIS-SULFUR LIGATION TO THE HEME OF BACTERIOFERRITIN, Journal of the American Chemical Society, 115(17), 1993, pp. 7716-7718
X-ray absorption spectroscopy was used to examine the ligation of the
heme of Azobacter vinelandii bacterioferritin scrupulously cleaned of
non-heme iron. We find that the iron of the protoporphyrin IX of the p
rotein has two axial sulfur ligands at 2.35 angstrom, with four nitrog
en ligands at 1.97 angstrom. This result confirms the previous suggest
ion of Cheesman et al. (Nature 1990, 346, 771-773; Biochem. J. 1992, 2
86, 361-367.), on the basis of less direct spectroscopic techniques, t
hat the heme of bacterioferritin is ligated by a pair of methionine li
gands. To date, this mode of coordination is unknown in any other heme
protein.