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Applied and Environmental Microbiology, June 2006, p. 4154-4162, Vol. 72, No. 6
0099-2240/06/$08.00+0 doi:10.1128/AEM.02696-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Kenji Saito,1,
Shun-Ichi Tanaka,1
Yuichi Koga,1
Masaaki Morikawa,1,
Kazufumi Takano,1,2 and
Shigenori Kanaya1*
Department of Material and Life Science, Graduate School of Engineering, Osaka University,1 PRESTO, JST, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan2
Received 15 November 2005/ Accepted 1 April 2006
Subtilisin from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 is a member of the subtilisin family. T. kodakaraensis subtilisin in a proform (T. kodakaraensis pro-subtilisin), as well as its propeptide (T. kodakaraensis propeptide) and mature domain (T. kodakaraensis mat-subtilisin), were independently overproduced in E. coli, purified, and biochemically characterized. T. kodakaraensis pro-subtilisin was inactive in the absence of Ca2+ but was activated upon autoprocessing and degradation of propeptide in the presence of Ca2+ at 80°C. This maturation process was completed within 30 min at 80°C but was bound at an intermediate stage, in which the propeptide is autoprocessed from the mature domain (T. kodakaraensis mat-subtilisin*) but forms an inactive complex with T. kodakaraensis mat-subtilisin*, at lower temperatures. At 80°C, approximately 30% of T. kodakaraensis pro-subtilisin was autoprocessed into T. kodakaraensis propeptide and T. kodakaraensis mat-subtilisin*, and the other 70% was completely degraded to small fragments. Likewise, T. kodakaraensis mat-subtilisin was inactive in the absence of Ca2+ but was activated upon incubation with Ca2+ at 80°C. The kinetic parameters and stability of the resultant activated protein were nearly identical to those of T. kodakaraensis mat-subtilisin*, indicating that T. kodakaraensis mat-subtilisin does not require T. kodakaraensis propeptide for folding. However, only
5% of T. kodakaraensis mat-subtilisin was converted to an active form, and the other part was completely degraded to small fragments. T. kodakaraensis propeptide was shown to be a potent inhibitor of T. kodakaraensis mat-subtilisin* and noncompetitively inhibited its activity with a Ki of 25 ± 3.0 nM at 20°C. T. kodakaraensis propeptide may be required to prevent the degradation of the T. kodakaraensis mat-subtilisin molecules that are activated later by those that are activated earlier.
M. Pulido and K. Saito contributed equally to this work.
Present address: Laboratory of Environmental Molecular Biology, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan.
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