@article {2469, title = {Metal binding to the tetrathiolate motif of desulforedoxin and related polypeptides}, journal = {Journal of Biological Inorganic Chemistry}, volume = {3}, number = {6}, year = {1998}, note = {

Times Cited: 6

}, month = {Dec}, pages = {643-649}, abstract = {

Desulforedoxin and the N-terminus of desulfoferrodoxin share a 36 amino acid domain containing a (Cys-S)(4) metal binding site. Recombinant forms of desulforedoxin, an N-terminal fragment of desulfoferrodoxin, and two desulforedoxin mutant proteins were reconstituted with Fe3+ Cd2+, and Zn2+ and relative metal ion affinities assessed by proton titrations. Protons compete with metal for protein ligands, a process that can be followed by monitoring the optical spectrum of the metal-protein complex as a function of pH. For all polypeptides, Fe3+ bound with the highest affinity, whereas the affinity of Zn2+ was greater than Cd2+ in desulforedoxin and the N-terminal fragment of desulfoferrodoxin, but this order was reversed in desulforedoxin mutant proteins. Metal binding in both mutants was significantly impaired. Furthermore, the Fe3+ complex of both mutants underwent a time-dependent bleaching process which coincided with increased reactivity of cysteine residues to Ellman{\textquoteright}s reagent and concomitant metal dissociation. It is hypothesized that this results from an autoredox reaction in which Fe3+ is reduced to Fe2+ with attendant oxidation of ligand thiols.

}, isbn = {0949-8257}, url = {http://dx.doi.org/10.1007/s007750050278}, author = {Kennedy, M. and Yu, L. and Lima, M. J. and Ascenso, C. S. and Czaja, C. and Moura, I. and Moura, J. J. G. and Rusnak, F.} }