Thermoacidophilic Archaebacteria Contain Bacterial‐Type Ferredoxins Acting as Electron Acceptors of 2‐Oxoacid: Ferredoxin Oxidoreductases

Abstract

Thermoplasma acidophilum and Sulfolobus acidocaldarius contain coenzyme A‐acylating 2‐oxoacid: ferredoxin oxidoreductases similar to those found in halophilic archaebacteria. A common feature of these enzymes is the formation of a free radical intermediate in the course of the catalytic cycle. The electron‐accepting ferredoxins and a similar protein from Desulfurococcus mobilis have been purified and characterized. In contrast to the [2Fe‐2S] ferredoxin of Halobacterium halobium, the ferredoxins of thermoacidophilic archaebacteria most likely contain two [4Fe‐4S]2+(2+,1+) clusters per molecule. Properties of these proteins are compared with respect to the evolution of archaebacteria. Copyright © 1982, Wiley Blackwell. All rights reserved