Contribution of the C-terminal region to the thermostability of the archaeal group II chaperonin from Thermococcus sp. strain KS-1.
Chaperonin is a double ring-shaped oligomeric protein complex, which captures a protein in the folding intermediate state and assists its folding in an ATP-dependent manner. The chaperonin from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1, is a group II chaperonin and is composed of two distinct subunits, alpha and beta. Although these subunits are highly homologous in sequence, the homo-oligomer of the beta-subunit is more thermostable than that of the alpha-subunit. To identify the region responsible for this difference in thermostability, we constructed domain-exchange mutants. The mutants containing the equatorial domain of the beta-subunit were more resistant to thermal dissociation than the mutants with that of the alpha-subunit. Thermostability of a beta-subunit mutant whose C-terminal 22 residues were replaced with those of the alpha-subunit decreased to the comparable level of that of the alpha-subunit homo-oligomer. These results indicate that the difference in thermostability between alpha- and beta-subunits mainly originates in the C-terminal residues in the equatorial domain, only where they exhibit substantial sequence difference.
Yoshida
Takao
T
Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 184-8588 Koganei, Tokyo, Japan. yohda@cc.tuat.ac.jp
Kanzaki
Taro
T
Iizuka
Ryo
R
Komada
Toshihiro
T
Zako
Tamotsu
T
Suzuki
Rintaro
R
Maruyama
Tadashi
T
Yohda
Masafumi
M