| Abstract: |
THERE is evidence to suggest that components of archaebacteria are evolutionarily related to cognates in the eukaryotic cytosol-7. We postulated that the major heat-shock protein of the thermophilic archaebacterium, Sulfolobus shibatae, is a molecular chaperone and that it is related to an as-yet unidentified chaperone component in the eukaryotic cytosol. Acquired thermotolerance in S. shibatae correlates with the predominant synthesis of this already abundant protein, referred to as thermophilic factor 55 (TF55; ref. 8). TF55 is a homo-oligomeric complex of two stacked 9-membered rings, closely resembling the 7-membered-ring complexes of the chaperonins, groEL, hsp60 and Rubisco-binding protein9-15. The TF55 complex binds unfolded polypeptides in vitro and has ATPase activity - features consistent with its being a molecular chaperone16,17. The primary structure of TF55, however, is not significantly related to the chaperonins. On the other hand, it is highly homologous (36-40% identity) to a ubiquitous eukaryotic protein, t-complex polypeptide-1 (TCP1; refs 18-20). In Saccharomyces cerevisiae, TCP1 is an essential protein that may play a part in mitotic spindle formation21. We suggest that TF55 in archaebacteria and TCP1 in the eukaryotic cytosol are members of a new class of molecular chaperones. © 1991 Nature Publishing Group. |
| Keywords: |
unclassified drug; dna-binding proteins; nonhuman; animal; mice; bacteria (microorganisms); nuclear proteins; bacterial proteins; amino acid sequence; molecular sequence data; saccharomyces cerevisiae; eukaryota; base sequence; temperature; sequence homology, nucleic acid; archaebacterium; archaea; heat tolerance; heat-shock proteins; heat shock protein; thermophilic bacterium; sulfolobus; sulfolobus shibatae; priority journal; article; support, non-u.s. gov't; support, u.s. gov't, p.h.s.; support, u.s. gov't, non-p.h.s.; adenosinetriphosphatase; chaperonin; thermophilic factor
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