Effect of the C-terminal truncation on the functional cycle of chaperonin groel: Implication that th
June 29th, 2008 | by admin |Effect of the C-terminal truncation on the functional cycle of chaperonin groel: Implication that the C-terminal region facilitates the transition from the folding-arrested to the folding-competent state.
To elucidate the exact role of the C-terminal region of GroEL in its functional cycle, the C-terminal 20 amino acids truncated mutant of GroEL was constructed. Steady-state ATPase rate and duration of GroES binding showed that the functional cycle of the truncated GroEL is extended by ~2 s in comparison with that of the wild-type, without interfering with the basic functions of GroEL. We have proposed a model for the functional cycle of GroEL, which consists of two rate-limiting steps of ~3 s and ~5 s duration (Ueno, T., Taguchi, H., Tadakuma, H., Yoshida, M., and Funatsu, T. (2004) Molecular Cell 14, 423-434). According to the model, detailed kinetic studies were performed. We found that a 20 residue truncation of the C-terminus extends the time until inorganic phosphate is generated, and the time for arresting protein folding in the central cavity, i.e. the lifetime of the first rate-limiting step in the functional cycle, to ~5 s duration. These results suggest that the integrity of the C-terminal region facilitates the transition from the first to the second rate-limiting state.
Suzuki M, Ueno T, Iizuka R, Miura T, Zako T, Akahori R, Miyake T, Shimamoto N, Aoki M, Tanii T, Ohdomari I, Funatsu T.
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033.