A molecular chaperone from a thermophilic archaebacterium is related to the eukaryotic protein t-complex polypeptide-1.
There is evidence to suggest that components of archaebacteria are evolutionarily related to cognates in the eukaryotic cytosol. 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). 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 protein. The TF55 complex binds unfolded polypeptides in vitro and has ATPase activity-features consistent with its being a molecular chaperone. 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). In Saccharomyces cerevisiae, TCP1 is an essential protein that may play a part in mitotic spindle formation. We suggest that TF55 in archaebacteria and TCP1 in the eukaryotic cytosol are members of a new class of molecular chaperones.
Trent
J D
JD
Howard Hughes Medical Institute, Yale School of Medicine, New Haven, Connecticut 06510.
Nimmesgern
E
E
Wall
J S
JS
Hartl
F U
FU
Horwich
A L
AL
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019843:Archaeal Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008869:Microtubule-Associated Proteins; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D016944:Sulfolobus / Q000235:genetics*; D013696:Temperature; D044767:Ubiquitin-Protein Ligases; D056427:t-Complex Genome Region
D019843:Archaeal Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; C072010:TF55 protein, Sulfolobus shibatae; C116196:PPP1R11 protein, human; D044767:Ubiquitin-Protein Ligases; D000251:Adenosine Triphosphatases