-transparent.png){kind=logo}
Room temperature circular dichroism (CD) and low temperature magnetic circular dichroism (MCD) spectra of air-oxidized and dithionite-reduced Azotobacter vinelandii ferredoxin I (FdI), a [( 4Fe-4S]2+/1+, [3Fe-4S]1+/0) protein, are reported. Unlike the CD of oxidized FdI, the CD of dithionite-reduced FdI exhibits significant pH dependence, consistent with protonation-deprotonation at or near the cluster reduced: the [3Fe-4S] cluster. The MCD of reduced FdI, which originates in the paramagnetic reduced [3Fe-4S]0 cluster, is also pH-dependent. Detailed studies of the field dependence and temperature dependence of the MCD of oxidized and reduced FdI, in the latter case at pH 6.0 and 8.3, are reported. The low-field temperature dependence of the MCD of oxidized FdI, which originates in the paramagnetic oxidized [3Fe-4S]1+ cluster, establishes the absence of a significant population of excited electronic states of this cluster up to 60 K. The low-field temperature dependence of the MCD of reduced FdI establishes that the ground-state manifold of the reduced [3Fe-4S]0 cluster possesses S greater than or equal to 2 at both pH 6.0 and 8.3. Analysis, assuming S = 2 and an axial zero-field splitting Hamiltonian, leads to D = -2.0 and -3.5 cm-1 at pH 6.0 and 8.3, respectively. The site of the (de)protonation affecting the spectroscopic properties of the [3Fe-4S] cluster remains unknown.
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
May 1981,
Biochemistry,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
February 1994,
Protein expression and purification,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
February 1988,
Proceedings of the National Academy of Sciences of the United States of America,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
December 1981,
The Journal of biological chemistry,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
December 1994,
Biochemistry,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
September 1992,
The Biochemical journal,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
January 1988,
The Journal of biological chemistry,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
April 1984,
Proceedings of the National Academy of Sciences of the United States of America,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
January 1999,
The Journal of biological chemistry,
P J Stephens, and
G M Jensen, and
F J Devlin, and
T V Morgan, and
C D Stout, and
A E Martin, and
B K Burgess
May 1981,
The Journal of biological chemistry,
