Potentiometric titration of the high- and low-potential 4Fe-4S* centers of Azotobacter vinelandii ferredoxin I.
نویسندگان
چکیده
The high-potential 4Fe-4S* center ofAzotobacter vinelandii ferredoxin I has been titrated potentiometrically by a reductive procedure. The absorbance decrease at 510 nm accompanying the reduction of the high-potential center titrated with an Em of 320 mV (n = 1). The low-potential 4Fe-4S* center was titrated by using the absorbance decrease at 410 nm to monitor its reduction. This center exhibited an Em of -424 mV (n = 1).
منابع مشابه
High and low reduction potential 4Fe-4S clusters in Azotobacter vinelandii (4Fe-4S) 2ferredoxin I. Influence of the polypeptide on the reduction potentials.
Azotobacter vinelandii (4Fe-4S)2 ferredoxin I (Fd I) is an electron transfer protein with Mr equals 14,500 and Eo equals -420 mv. It exhibits and EPR signal of g equals 2.01 in its isolated form. This resonance is almost identical with the signal that originates from a "super-oxidized" state of the 4Fe-4S cluster of potassium ferricyanide-treated Clostridium ferredoxin. A cluster that exhibits ...
متن کاملInfluence of electrochemical properties in determining the sensitivity of [4Fe-4S] clusters in proteins to oxidative damage.
Interconversion between [4Fe-4S] cubane and [3Fe-4S] cuboidal states represents one of the simplest structural changes an iron-sulphur cluster can undertake. This reaction is implicated in oxidative damage and in modulation of the activity and regulation of certain enzymes, and it is therefore important to understand the factors governing cluster stability and the processes that activate cluste...
متن کاملSite-directed mutagenesis of Azotobacter vinelandii ferredoxin I: [Fe-S] cluster-driven protein rearrangement.
Azotobacter vinelandii ferredoxin I is a small protein that contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. Recently the x-ray crystal structure has been redetermined and the fdxA gene, which encodes the protein, has been cloned and sequenced. Here we report the site-directed mutation of Cys-20, which is a ligand of the [4Fe-4S] cluster in the native protein, to alanine and the characte...
متن کاملAzotobacter chroococcum 7Fe ferredoxin. Two pH-dependent forms of the reduced 3Fe clusters and its conversion to a 4Fe cluster.
Ferredoxin from Azotobacter chroococcum has been studied by low-temperature magnetic-circular-dichroism and electron-paramagnetic-resonance spectroscopy. When aerobically isolated ferredoxin contains a [3Fe-4S] and [4Fe-4S] cluster. Anaerobic treatment with dithionite in the presence of ethanediol reduces the [3Fe-4S] cluster to give two spectroscopically distinct forms RI and RII which are rev...
متن کاملStructure of a 7Fe ferredoxin from Azotobacter vinelandii.
The structure of the 7Fe ferredoxin from Azotobacter vinelandii has been solved from a 3.0-A multiple isomorphous replacement map. The crystals belong to space group P43212 with a = 55.22, c = 95.20 A, and Z = 1. Heavy-atom derivatives were prepared with K2PtCl4,K2[OsO2(OH)4], and Na3RhCl6. Anomalous scattering data were collected for native (Fe) and Pt derivative crystals. The figure of merit ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of bacteriology
دوره 136 2 شماره
صفحات -
تاریخ انتشار 1978