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Nested allosteric interactions in the cytoplasmic chaperonin containing TCP-1.
G Kafri1, K R Willison, A Horovitz
1Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
Protein Science : a Publication of the Protein Society
|March 27, 2001
Summary
Chaperonin containing TCP-1 (CCT) exhibits distinct allosteric transitions during ATP hydrolysis, suggesting nested cooperativity in double-ring chaperones.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Folding
Background:
- Chaperonins are essential molecular machines that assist protein folding.
- The chaperonin containing TCP-1 (CCT) is a key eukaryotic chaperonin involved in protein folding.
- Understanding CCT's mechanism, particularly its ATP hydrolysis activity, is crucial for elucidating its function.
Purpose of the Study:
- To investigate the allosteric behavior of bovine testis CCT during ATP hydrolysis.
- To determine the cooperativity patterns of ATP hydrolysis in CCT.
Main Methods:
- Measurement of initial rates of ATP hydrolysis by CCT.
- Analysis of ATP hydrolysis rates as a function of ATP concentration.
Main Results:
- Two distinct allosteric transitions were observed in ATP hydrolysis rates at low (<100 microM) and high ATP concentrations.
- CCT displays positive intra-ring cooperativity and negative inter-ring cooperativity in ATP hydrolysis.
- Weak positive intra-ring cooperativity in CCT may stem from subunit heterogeneity.
Conclusions:
- Nested allosteric behavior is likely a common feature of double-ring chaperone systems like CCT.
- The observed cooperativity patterns provide insights into the functional mechanism of CCT.