Spectroscopic investigation of selective cluster conversion of archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7.
Archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7 contains one [3Fe-4S] cluster (cluster I), one [4Fe-4S] cluster (cluster II), and one isolated zinc center. Oxidative degradation of this ferredoxin led to the formation of a stable intermediate with 1 zinc and approximately 6 iron atoms. The metal centers of this intermediate were analyzed by electron paramagnetic resonance (EPR), low temperature resonance Raman, x-ray absorption, and (1)H NMR spectroscopies. The spectroscopic data suggest that (i) cluster II was selectively converted to a cubane [3Fe-4S](1+) cluster in the intermediate, without forming a stable radical species, and that (ii) the local metric environments of cluster I and the isolated zinc site did not change significantly in the intermediate. It is concluded that the initial step of oxidative degradation of the archaeal zinc-containing ferredoxin is selective conversion of cluster II, generating a novel intermediate containing two [3Fe-4S] clusters and an isolated zinc center. At this stage, significant structural rearrangement of the protein does not occur. We propose a new scheme for oxidative degradation of dicluster ferredoxins in which each cluster converts in a stepwise manner, prior to apoprotein formation, and discuss its structural and evolutionary implications.
Iwasaki
T
T
Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Tokyo, Japan. iwasaki/biochem@om.nms.ac.jp
Watanabe
E
E
Ohmori
D
D
Imai
T
T
Urushiyama
A
A
Akiyama
M
M
Hayashi-Iwasaki
Y
Y
Cosper
N J
NJ
Scott
R A
RA
D002847:Chromatography, Agarose; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry* / Q000378:metabolism*; D007501:Iron / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D013052:Spectrometry, X-Ray Emission; D013059:Spectrum Analysis, Raman; D016944:Sulfolobus / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D005288:Ferredoxins; D007501:Iron; D015032:Zinc; D010100:Oxygen