F. Nunzi et al., ACTIVE-SITE GEOMETRY IN THE HIGH OXIDOREDUCTION POTENTIAL RUSTICYANINFROM THIOBACILLUS-FERROOXIDANS, Biochemical and biophysical research communications, 203(3), 1994, pp. 1655-1662
Rusticyanin is a blue copper protein involved in the oxidation of iron
catalyzed by Thiobacillus ferrooxidans. This protein is characterized
by a high oxide-reduction potential and a high stability at low pH. T
he three dimensional structure of this protein is still unknown and in
order to investigate the geometric properties of the copper center wh
ich could be correlated to the high oxide-reduction potential, we have
studied rusticyanin by UV-Visible, EPR and NMR spectroscopies, at dif
ferent pH values. Our results suggest that rusticyanin is stable betwe
en pH 2 and pH 9 and that the copper center does not undergo significa
nt geometric modifications in this pH range. Moreover, the copper atom
could be buried more deeply in the protein than in other type I coppe
r proteins and the atomic distance Cu-S(Met), one of the four bonds in
volved in copper coordination, is probably shorter in rusticyanin than
in other cupredoxins. These two properties of the copper site are exp
ected to be responsible, in part, for the high oxide-reduction potenti
al observed in rusticyanin. (C) 1994 Academic Press, Inc.