A novel ATPase complex selectively accumulated upon heat shock is a major cellular component of thermophilic archaebacteria.

Abstract

We have discovered a large cylindrical protein complex which is an abundant component of the cytoplasm of extremely thermophilic archaebacteria. Structural analysis by image processing of electron micrographs suggests that the complex is composed of two stacked rings of eight subunits each; the rings enclose a central channel. The complex purified from the hyperthermophile Pyrodictium occultum is composed of equal quantities of two polypeptides of Mr 56,000 and 59,000. It exhibits an extremely thermostable ATPase activity with a temperature optimum of 100 degrees C. The basal level of the ATPase complex in the cell is high, and it becomes highly enriched as a result of heat shock (shift from 102 degrees C to 108 degrees C) or balanced growth at temperatures near the physiological upper limit. Immunoblotting results indicate that a related protein is present in most thermophilic archaebacteria and in Escherichia coli. This protein complex may play an important role in the adaptation of thermophilic archaebacteria to life at high temperature.

A novel aminopeptidase associated with the 60 kDa chaperonin in the thermophilic archaeon Sulfolobus solfataricus

“…The chaperonin complex is very abundant in S. shibatae cells under normal growth conditions, and is further increased upon heat shock, namely exposure of the cells to a temperature of 86-88ЊC (Trent et al, 1990). Similar hetero-oligomeric chaperonin complexes have also been described in other Archaea (Phipps et al, 1991;Knapp et al, 1994;Waldmann et al, 1995).…”

The Thermosome of Thermoplasma acidophilum and Its Relationship to the Eukaryotic Chaperonin TRiC

“…It was difficult to assess the symmetry of the archaebacterial chaperonins in an unambiguous manner: In the case of TF55, most of the particles showed ninefold symmetry 'but some eightfold symmetrical complexes were also seen' [15]. With the thermosome of P. occulturn, which is composed of two types of subunits in a 1 : 1 stoichiometry, correlation averaging revealed an eightfold pseudo symmetry but a significant subgroup (< 10% of the total data set) appeared to have ninefold symmetry [16]. In an attempt to clarify the situation, we have subjected a large data set of TF55-like particles from S. solfataricus to three different image-analysis procedures performed independently in three different laboratories [17].…”

“…The thermophilic factor 55 (TF55) of Suvolobus shibatae [I51 and the thermosome of Pyrodictium occultum [16] have been identified as members of a related family of high molecular-mass ATPase complexes (Mr approximately I@) which are also able to bind denatured polypeptides and are ubiquitously present in the archea [16]. TF55 is built up by one type of protein subunit only (Mr 5 9 , whereas the thermosome of l?…”

“…Transmission electron microscopy of negatively stained particles in conjunction with image processing has shown that these molecules consist of two stacked rings with nine subunits each in the case of Sulfolobus [15, 171. In the case of Pyrodictium, particles with eight subunits in each of the two rings were predominant [16,181, suggesting that they have pseudo eightfold symmetry. However, a small subpoulation showed indications of a different symmetry.…”

Recombinant homo‐ and hetero‐oligomers of an ultrastable chaperonin from the archaeon Pyrodictium occultum show chaperone activity in vitro

“…The high-molecular-mass fractions were pooled and stored at Ϫ20°C. The natural thermosome was isolated from P. occultum as described by Phipps et al [4].…”