Michael W. W. Adams
Professor of Biochemistry & Molecular Biology and MicrobiologyCo-Director, Center for Metalloenzyme Studies
Professor Adams obtained his B.Sc. in 1976 and his Ph.D. in 1979 both from the University of London. He performed postdoctoral research at Purdue University and was employed at the Corporate Research Laboratories of Exxon Research and Engineering Co. before moving to the University of Georgia in 1987. He became Professor of Biochemistry & Molecular Biology and adjunct Professor of Microbiology in 1994, and Research Professor in 1996.
Our research concerns "hyperthermophiles" which are a recently discovered group of microorganisms that have the remarkable property of growing at temperatures near and even above 100°C. They have been isolated from volcanically-heated environments including deep sea hydrothermal vents. Virtually all of them are classified as "archaea" (formerly archaebacteria) rather than as bacteria, and they represent the most slowly evolving or "ancient" form of life known. They support the hypothesis that life first evolved on this planet under extreme temperatures, and that all conventional life forms growing near ambient temperature are adaptations from hyperthermophilic-type organisms.
Most of the twenty or so genera of hyperthermophiles known grow by fermenting peptides and sugars and by reducing elemental sulfur to hydrogen sulfide. We grow several hyperthermophiles in large scale culture (600 liter) and have purified from them a range of enzymes mainly of the oxidoreductase-type. These are involved in unusual pathways for sugar and peptide utilization and for sulfur reduction. The proteins are being examined by a variety of biochemical, spectroscopic, crystallographic and recombinant DNA techniques. These include hydrogenases, redox proteins such as ferredoxin and rubredoxin, four distinct iron-sulfur-containing keto-acid oxidoreductases which are involved in amino acid oxidation, and three different aldehyde-oxidizing enzymes that contain the metal tungsten. Tungsten is seldom used in biological systems but its chemical properties make well suited to catalyze electron-transfer reactions at extreme temperatures. Hence, the hyperthermophiles are the only known organisms whose growth is obligately dependent upon this unusual metal.
In collaborative crystallographic studies, one of the tungstoenzymes we had purified recently provided the first three-dimensional structure for an enzyme from a hyperthermophile. We had earlier obtained the first three dimensional structure of a hyperthermophilic electron transfer protein. Remarkably, comparisons with similar proteins from organisms growing at more conventional temperatures showed that their structures were virtually identical. It therefore appears that protein hyperthermostability is not due to gross differences, rather, very subtle effects in protein structure can lead to dramatic differences in thermal stability. Site-directed mutagenesis techniques are now being utilized to investigate enzyme catalysis and electron transfer pathways near 100°C, as well as mechanisms of protein "hyperthermostability".
This research is supported by the US Department of Energy, the National Science Foundation, the US Department of Agriculture, and the National Institutes of Health.
"Oxidoreductase-type enzymes and redox proteins involved in the fermentative metabolisms of hyperthermophilic archaea," Adams, M. W. W. and Kletzin, A. Advs. Prot. Chem 1996, 48, 101-180.
"Tungstoenzymes," Johnson, M. K.; Rees, D. C.; Adams, M. W. W. Chem. Rev. 1996, 96, 2817-2839.
E-mail contact:
adams@bmb.uga.edu
