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Updated: Aug 14, 2026

Use of Stopped-Flow Fluorescence and Labeled Nucleotides to Analyze the ATP Turnover Cycle of Kinesins
Published on: October 17, 2014
ATPase cycle of an archaeal chaperonin
I Gutsche1, O Mihalache, W Baumeister
1Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, Martinsried, D-82152, Germany. gutsche@biochem.mpg.de
Abstract:
Recent structural data imply differences in allosteric behavior of the group I chaperonins, typified by GroEL from Escherichia coli, and the group II chaperonins, which comprise archaeal thermosome and eukaryotic TRiC/CCT. Therefore, this study addresses the mechanism of interaction of adenine nucleotides with recombinant alpha-only and native alphabeta-thermosomes from Thermoplasma acidophilum, which also enables us to analyze the role of the heterooligomeric composition of the natural thermosome. Although all subunits of the alpha-only thermosome seem to bind nucleotides tightly and independently, the native chaperonin has two different classes of ATP-binding sites. Furthermore, for the alpha-only thermosome, the steady-state ATPase rate is determined by the cleavage reaction itself, whereas, for the alphabeta-thermosome, the rate-limiting step is associated with a post-hydrolysis isomerisation into a non-covalent ADP*P(i) species prior to the release of the gamma-phosphate group. After half-saturation with ATP, a negative cooperativity in hydrolysis is observed for both thermosomes. The effect of Mg(2+) and K(+) nucleotide cycling is documented. We conclude that archaeal chaperonins have unique allosteric properties and discuss them in the light of the mechanism established for the group I chaperonins.
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