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
Journal
European Journal of Biochemistry
Journal Volume
231
Journal Issue
1
Pages
149-156
Date Issued
1995
Author(s)
Abstract
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 12959 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. Cysl9 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. Copyright © 1995, Wiley Blackwell. All rights reserved
Type
journal article