Open Access[4Fe-4S]-cluster-depleted Azotobacter vinelandii ferredoxin I: a new 3Fe iron-sulfur protein.
Author(s) -
Philip J. Stephens,
Túlio Morgan,
F. J. Devlin,
James E. PennerHahn,
Keith O. Hodgson,
Robert A. Scott,
C.D. Stout,
Barbara K. Burgess
Publication year - 1985
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.82.17.5661
Subject(s) - azotobacter vinelandii , chemistry , ferredoxin , electron paramagnetic resonance , iron–sulfur cluster , cluster (spacecraft) , extended x ray absorption fine structure , crystallography , absorption (acoustics) , absorption spectroscopy , inorganic chemistry , nuclear magnetic resonance , materials science , organic chemistry , physics , nitrogenase , quantum mechanics , nitrogen fixation , computer science , nitrogen , programming language , composite material , enzyme
Fe(CN)6(-3) oxidation of the aerobically isolated 7Fe Azotobacter vinelandii ferredoxin I, (7Fe)FdI, is a degradative reaction. Destruction of the [4Fe-4S] cluster occurs first, followed by destruction of the [3Fe-3S] cluster. At a Fe(CN)6(-3)/(7Fe)FdI concentration ratio of 20, the product is a mixture of apoprotein and protein containing only a [3Fe-3S] cluster, (3Fe)FdI. This protein mixture, after partial purification, has been characterized by absorption, CD, magnetic CD, and EPR and Fe x-ray absorption spectroscopies. EPR and magnetic CD spectra provide strong evidence that the [3Fe-3S] cluster in (3Fe)FdI is essentially identical in structure to that in (7Fe)FdI. Analysis of the extended x-ray absorption fine structure (EXAFS) of (3Fe)FdI finds Fe scattering at an average Fe...Fe distance of approximately equal to 2.7 A. The structure of the oxidized [3Fe-3S] cluster in solutions of oxidized (3Fe)FdI, and, by extension, of oxidized (7Fe)FdI, is thus different from that obtained by x-ray crystallography on oxidized (7Fe)FdI. Possible interpretations of this result are discussed.