Amino acid sequence of spinach ferredoxin:thioredoxin reductase catalytic subunit and identification of thiol groups constituting a redox-active disulfide and a [4Fe-4S] cluster.
Ferredoxin:thioredoxin reductase is a [4Fe-4S] protein involved in the light regulation of carbon metabolism in oxygenic photosynthesis. This enzyme catalyses the reduction of thioredoxins with light-generated electrons. Ferredoxin:thioredoxin reductase is composed of two dissimilar subunits, a catalytic subunit, and a variable subunit. The catalytic subunit of spinach ferredoxin:thioredoxin reductase, which contains the redox-active disulfide bridge, was sequenced by conventional protein sequencing techniques and the functional roles of all eight cysteine residues were examined by chemical modifications. The polypeptide chain with a calculated molecular mass of 12,959 Da consists of 113 amino acids and has a calculated isoelectric point of 5.30. Six of the eight cysteine residues are clustered as Cys-Pro-Cys and Cys-His-Cys groups. Cys19 and Cys27 are free cysteines with no catalytic function, Cys54 and Cys84 constitute the redox-active disulfide bridge of the active site, and the remaining four, Cys52, Cys71, Cys73, and Cys82 bind the Fe-S cluster.
Chow
L P
LP
Research Institute for Biosciences, Science University of Tokyo, Japan.
Iwadate
H
H
Yano
K
K
Kamo
M
M
Tsugita
A
A
Gardet-Salvi
L
L
Stritt-Etter
A L
AL
Schürmann
P
P
D000595:Amino Acid Sequence; D002384:Catalysis; D004220:Disulfides / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D018724:Spinacia oleracea / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D004220:Disulfides; D007506:Iron-Sulfur Proteins; D013438:Sulfhydryl Compounds; D010088:Oxidoreductases; C021588:ferredoxin-thioredoxin reductase