PRESSURE STABILIZATION OF PROTEINS FROM EXTREME THERMOPHILES

We describe the stabilization by pressure of enzymes, including a hydr ogenase from Methanococcus jannaschii, an extremely thermophilic deep- sea methanogen. This is the first published report of proteins from th ermophiles being stabilized by pressure. Inactivation studies of parti ally purified hydrogenases from an extreme thermophile (Methanococcus igneus), a moderate thermophile (Methanococcus thermolithotrophicus), and a mesophile (Methanococcus maripaludis), all from shallow marine s ites, show that pressure stabilization is not unique to enzymes isolat ed from high-pressure environments. These studies suggest that pressur e stabilization of an enzyme may be related to its thermophilicity. Fu rther experiments comparing the effects of increased pressure on the s tability of alpha-glucosidases from the hyperthermophile Pyrococcus fu riosus and Saccharomyces cerevisiae support this possibility. We hale also examined pressure effects on several highly homologous glyceralde hyde-3-phosphate dehydrogenases from mesophilic and thermophilic sourc es and a rubredoxin from P. furiosus. The results suggest that hydroph obic interactions, which have been implicated in the stabilization of many thermophilic proteins, contribute to the pressure stabilization o f enzymes from thermophiles.