REPORT DOCUMENTATION PAGE Form Approved QMB NO. 0704-0188 Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for information Operations and Reports, 1215 Jefferson Davis Highway Suite 1204. Arlington, VA 22202-4302. and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188.) Washington DC 20501 1. AGENCY USE ONLY (Leave Blank) REPORT DATE 9/16/98 4. TITLE AND SUBTITLE Crystal Structure of an Alcohol Dehydrogenase from the Extreme Thermophile Thermoanaerobium brockii AUTHOR(S) Menachem Shoham 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) ; Case Western Reserve University Cleveland, OH 44106-4935 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) U. S. Army Research Office P.O.Box 12211 Research Triangle Park, NC 27709-2211 3. REPORT TYPE AND DATES COVERED Final Progress Report 5. FUNDING NUMBERS DAAH04-95-1-0396 8. PERFORMING ORGANIZATION REPORT NUMBER 642-3043 10. SPONSORING / MONITORING AGENCY REPORT NUMBER ARO 34095.2-LS 11. SUPPLEMENTARY NOTES The views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy or decision, unless so designated by the documentation. 12 a. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited. 12 b. DISTRIBUTION CODE 13. ABSTRACT (Maximum 200 words) The crystal structure of a thermophilic alcohol dehydrogenase (TBAD) has been determined in complex with sec- butanol as substrate to a resolution of 3.0 Ä. The enzyme is from Thermoanaerobacter brockii, a bacterium isolated from hot springs in Yellowstone National Park. This tetrameric enzyme has a melting temperature of 98 °C. The structure consists of two domains, the catalytic domain and the cofactor-binding domain, with the active site located in a deep cleft at the domain interface. Factors important for the thermostability have been deduced by comparison with the crystal structure of a highly homologous mesophilic alcohol dehydrogenase from Clostridium beijerinckii (CBAD). The thermophilic enzyme has a more hydrophilic exterior, a more hydrophobic interior, a smaller surface area, more prolines, alanines, and less serines than CBAD. Furthermore, in the thermophilic enzyme the number of all types of intersubunit interactions is increased: more salt bridges, hydrogen bonds and hydrophobic interactions. All these effects combined can account for the 32°C higher melting temperature of the thermophilic enzyme. 14. SUBJECT TERMS 19981230 012 17. SECURITY CLASSIFICATION OR REPORT UNCLASSIFIED NSN 7540-01-280-5500 18. SECURITY CLASSIFICATION ON THIS PAGE UNCLASSIFIED 19. SECURITY CLASSIFICATION OF ABSTRACT UNCLASSIFIED 15. NUMBER OF PAGES 27 16. PRICE CODE 20. LIMITATION OF ABSTRACT UL Standard Form 298 (Rev.2-89)