The binding sites of iron in rubredoxin from Micrococcus aerogenes.

Abstract
From the electron paramagnetic resonance (EPR) spectrum and its variation with pH, the sequence studies on the location of cysteine residues and the quantitative analysis of the number of -SH groups, it is suggested that the 1 ferric Fe in rubre-doxin is coordinately bonded in a rhombic symmetry to 4 -SH groups (provided by 4 cysteine residues) and possibly to tyrosine or lysine residues. The cysteine residues are located in positions, 6, 9, 38 and 41 in the rubredoxin molecule. The Fe may function not only as an electron acceptor but to stabilize the conformation of the molecule.