Open AccessChaperonin filaments: The archael cytoskeleton
Author(s) -
Jonathan D. Trent,
Hiromi Kagawa,
Takuro Yaoi,
Eric Olle,
Nestor J. Zaluzec
Publication year - 1997
Language(s) - English
Resource type - Reports
DOI - 10.2172/510354
Subject(s) - chaperonin , cytoskeleton , intracellular , microbiology and biotechnology , biology , protein subunit , biophysics , intermediate filament , protein filament , immunogold labelling , actin , biochemistry , chemistry , protein folding , cell , ultrastructure , anatomy , gene
Chaperonins are multi-subunit double-ring complexed composed of 60-kDa proteins that are believed to mediate protein folding in vivo. The chaperonins in the hyperthermophilic archaeon Sulfolobus shibatae are composed of the organism`s two most abundant proteins, which represent 4% of its total protein and have an intracellular concentration of {ge} 3.0 mg/ml. At concentrations of 1.0 mg/ml, purified chaperonin proteins aggregate to form ordered filaments. Filament formation, which requires Mg{sup ++} and nucleotide binding (not hydrolysis), occurs at physiological temperatures under conditions suggesting filaments may exist in vivo. If the estimated 4,600 chaperonins per cell, formed filaments in vivo, they could create a matrix of filaments that would span the diameter of an average S. shibatae cell 100 times. Direct observations of unfixed, minimally treated cells by intermediate voltage electron microscopy (300 kV) revealed an intracellular network of filaments that resembles chaperonin filaments produced in vitro. The hypothesis that the intracellular network contains chaperonins is supported by immunogold analyses. The authors propose that chaperonin activity may be regulated in vivo by filament formation and that chaperonin filaments may serve a cytoskeleton-like function in archaea and perhaps in other prokaryotes