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APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Feb. 2011, p. 14361442 Vol. 77, No. 4 0099-2240/11/$12.00 doi:10.1128/AEM.01802-10
 

Summary: APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Feb. 2011, p. 14361442 Vol. 77, No. 4
0099-2240/11/$12.00 doi:10.1128/AEM.01802-10
Copyright 2011, American Society for Microbiology. All Rights Reserved.
Comparison of Family 9 Cellulases from Mesophilic
and Thermophilic Bacteria
Florence Mingardon, John D. Bagert, Cyprien Maisonnier, Devin L. Trudeau, and Frances H. Arnold*
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
Received 28 July 2010/Accepted 4 December 2010
Cellulases containing a family 9 catalytic domain and a family 3c cellulose binding module (CBM3c) are
important components of bacterial cellulolytic systems. We measured the temperature dependence of the
activities of three homologs: Clostridium cellulolyticum Cel9G, Thermobifida fusca Cel9A, and C. thermocellum
Cel9I. To directly compare their catalytic activities, we constructed six new versions of the enzymes in which
the three GH9-CBM3c domains were fused to a dockerin both with and without a T. fusca fibronectin type 3
homology module (Fn3). We studied the activities of these enzymes on crystalline cellulose alone and in
complex with a miniscaffoldin containing a cohesin and a CBM3a. The presence of Fn3 had no measurable
effect on thermostability or cellulase activity. The GH9-CBM3c domains of Cel9A and Cel9I, however, were
more active than the wild type when fused to a dockerin complexed to scaffoldin. The three cellulases in
complex have similar activities on crystalline cellulose up to 60C, but C. thermocellum Cel9I, the most
thermostable of the three, remains highly active up to 80C, where its activity is 1.9 times higher than at 60C.
We also compared the temperature-dependent activities of different versions of Cel9I (wild type or in complex

  

Source: Arnold, Frances H. - Division of Chemistry and Chemical Engineering, California Institute of Technology

 

Collections: Chemistry; Biology and Medicine