NOVEL IRON-SULFUR CENTERS IN METALLOENZYMES AND REDOX PROTEINS FROM EXTREMELY THERMOPHILIC BACTERIA

This chapter describes the properties of a variety of Fe–S-containing proteins that have been purified from extremely thermophilic bacteria. Extreme thermophiles are defined as organisms that grow optimally at temperatures of 80°C and above. They are a relatively recent discovery in the microbial world. At the time this research began in 1988, no metalloenzyme had been isolated from these bacteria. As most of the extreme thermophiles metabolize molecular hydrogen (H2), the initial objective of the study described in the chapter was to characterize their hydrogenases, the enzymes responsible for catalyzing H2 oxidation and H2 production. Hydrogenases have been purified from several mesophilic organisms. All are thermolabile proteins containing Fe–S or Ni–Fe–S centers. Such [M–3Fe–4S] clusters in an extremely stable protein may prove useful as models for the catalytic sites of several Fe–S enzymes. Tungsten, an element seldom used in biology, stimulates the growth of Pyrococcus furiosus, and from it, a novel tungstopterin-containing Fe–S enzyme is characterized. © 1992, ACADEMIC PRESS, INC.