J. Biochem, 2001, Vol. 129, No. 1 173-178
© 2001 Japanese Biochemical Society
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Temperature Dependence of the Enzyme-Substrate Recognition Mechanism1
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*Department of Biology, Graduate School of Science, Osaka University Toyonaka, Osaka 560-0043
National Institute of Bioscience and Human-Technology Tsukuba, Ibaraki 305-8566
Genomic Sciences Center, RIKEN Yokohama Institute 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045
Harima Institute/SPring-8 1-1-1 Koto, Mikazuki-cho, Sayo-gun, Hyogo 679-5148
2To whom correspondence should be addressed. Tel: +81-6-6850-5433, Fax: +81-6-6850-5442, E-mail: kuramitu{at}bio.sci.osaka-u.ac.jp
We determined the crystal structure of the liganded form of 
-aminotransferase from a hyperthermophile, Pyrococcus horikoshii. This hyperthermophilic enzyme did not show domain movement upon binding of an acidic substrate, glutamate, except for a small movement of the -helix from Glu16 to Ala25. The 
-carboxyl group of the acidic substrate was recognized by Tyr70* without its side-chain movement, but not by positively charged Arg or Lys. Compared with the homologous enzymes from Thermus thermophilus HB8 and Escherichia coli, it was suggested that the more thermophilic the enzyme is, the smaller the domain movement is. This rule seems to be applicable to many other enzymes already reported.
1This work was supported in part by the TARA (Tsukuba Advanced Research Alliance) Sakabe project and by Grants-in-Aid for Scientific Research (Nos. 11878118 and 11169224) from the Ministry of Education, Science, Sports and Culture of Japan, and a research grant from the Japan Society for the Promotion of Science ("Research for the Future" Program, No. JSPS-RFTF96L00506). The coordinates for unliganded and glutamate forms of PhAT have been deposited in the RSCB Protein Data Bank as entries 1GD9 and 1GDE, respectively.