Skip Navigation

This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Request Permissions
Google Scholar
Right arrow Articles by Nishikori, S.
Right arrow Articles by Takagi, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Nishikori, S.
Right arrow Articles by Takagi, M.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

J. Biochem, 2004, Vol. 135, No. 4 525-532
© 2004 The Japanese Biochemical Society

BIOCHEMISTRY

Mutational Effects on O6-Methylguanine-DNA Methyltransferase from Hyperthermophile: Contribution of Ion-Pair Network to Protein Thermostability

Shingo Nishikori1, Kentaro Shiraki1, Kiyonobu Yokota1, Naoshige Izumikawa1, Shinsuke Fujiwara2, Hiroshi Hashimoto3, Tadayuki Imanaka4 and Masahiro Takagi*,1

1 School of Materials Science, Japan Advanced Institute for Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292; 2 Department of Bioscience, School of Science and Technology, Kwansei-Gakuin University, 2-1 Gakuen Sanda, Hyogo 669-1337; 3 Science of Biological Supermolecular Systems, Graduate School of Integrated Science, Yokohama City University, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045; and 4 Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510

Ion pairs have been considered to be general stabilizing factors in hyperthermophilic proteins, but the present experimental data cannot fully explain how ion pairs and ion-pair networks contribute to the stability. In this paper, we show experimental evidence that not all of the internal ion pairs contribute to the thermal and thermodynamic stability, using O6-methylguanine-DNA methyltransferase from Thermococcus kodakaraensis KOD1 (Tk-MGMT) as a model protein. Of three mutants in which an inter-helical ion pair was disrupted, only one mutant (E93A) was shown to be destabilized. {Delta}G of E93A was lower by ~4 kJ mol–1 than that of the wild type, and E93A unfolded one order of magnitude faster than did the wild type and other variants. Glu 93 has unique properties in forming an ion-pair network that bridges the N- and C-terminal domains and connects three helices in the protein interior.

* To whom correspondence should be addressed. Tel: +81-761-51-1650, Fax: +81-761-51-1655, E-mail: takagi{at}jaist.ac.jp


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 J BiochemHome page
S. Nishikori, K. Shiraki, M. Okanojo, T. Imanaka, and M. Takagi
Equilibrium and Kinetic Stability of a Hyperthermophilic Protein, O6-Methylguanine-DNA Methyltransferase under Various Extreme Conditions
J. Biochem., October 1, 2004; 136(4): 503 - 508.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.