These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Direct square-wave voltammetry of superoxidized [4Fe-4S]3+ aconitase and associated 3Fe/4Fe cluster interconversions.
    Author: Tong J, Feinberg BA.
    Journal: J Biol Chem; 1994 Oct 07; 269(40):24920-7. PubMed ID: 7929174.
    Abstract:
    We report a direct square-wave voltammetric study of the iron-sulfur enzyme, aconitase, at the pyrolytic graphite edge electrode. New and established redox driven reactions were observed and the equilibrium reduction potential for each couple was determined: E0'[3Fe-4S]1+/0 = -268 mV, E0'[4Fe-4S]2+/1+ = -450 mV, E0'[4Fe-4S]3+/2+ = +100 mV, E0'Linear Form = -281 mV, and putatively, E0'[3Fe-4S]0/2- congruent to -1000 mV, all versus normal hydrogen electrode. Most importantly we have directly observed the superoxidized [4Fe-4S]3+ form of aconitase (originally proposed by Emptage, M. H., Dreyer, J.-L., Kennedy, M. C., and Beinert, H. (1983) J. Biol. Chem. 258, 11106-11111) and directly followed its conversion to the [3Fe-4S]1+ form; this intermediate is required for the deactivation of aconitase. Without exogenous ferrous iron, [3Fe-4S]0 aconitase is apparently super-reduced at very negative potentials to the [3Fe-4S]2- form and the concomitant formation of [4Fe-4S]2+ aconitase was followed over time. It is the apparent decomposition of super-reduced [3Fe-4S]2- aconitase that provides the source of ferrous iron for the interconversion of [3Fe-4S]0 aconitase to the [4Fe-4S]2+ form. Voltammetry of free and substrate bound [4Fe-4S]2+ aconitase showed that the latter is less susceptible to oxidation but, surprisingly, has the same E0'[4Fe-4S]3+/2+.
    [Abstract] [Full Text] [Related] [New Search]