Thermobifida exoglucanase Cel6B is incompatible with the cellulosomal mode in contrast to endoglucanase Cel6A

Systems and Synthetic Biology 09/2010; 4(3):193-201. DOI: 10.1007/s11693-010-9056-1
Source: PubMed

ABSTRACT Cellulosomes are efficient cellulose-degradation systems produced by selected anaerobic bacteria. This multi-enzyme complex is assembled from a group of cellulases attached to a protein scaffold termed scaffoldin, mediated by a high-affinity protein-protein interaction between the enzyme-borne dockerin module and the cohesin module of the scaffoldin. The enzymatic complex is attached as a whole to the cellulosic substrate via a cellulose-binding module (CBM) on the scaffoldin subunit. In previous works, we have employed a synthetic biology approach to convert several of the free cellulases of the aerobic bacterium, Thermobifida fusca, into the cellulosomal mode by replacing each of the enzymes' CBM with a dockerin. Here we show that although family six enzymes are not a part of any known cellulosomal system, the two family six enzymes of the T. fusca system (endoglucanase Cel6A and exoglucanase Cel6B) can be converted to work as cellulosomal enzymes. Indeed, the chimaeric dockerin-containing family six endoglucanase worked well as a cellulosomal enzyme, and proved to be more efficient than the parent enzyme when present in designer cellulosomes. In stark contrast, the chimaeric family six exoglucanase was markedly less efficient than the wild-type enzyme when mixed with other T. fusca cellulases, thus indicating its incompatibility with the cellulosomal mode of action.

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Available from: David Wilson, Aug 26, 2015
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    • "The CBM2s of endocellulase Cel6A and exocellulase Cel6B were replaced with dockerins from C. cellulolyticum and C. thermocellum, producing chimeras 6A-c and t-6B. In general, activity was reduced on most substrates; however, surprisingly, t-6B showed about 14-fold higher activity on amorphous cellulose than the native enzyme (Caspi et al., 2006, 2008, 2011). Designer cellulosome harboring cellulases and xylanases was designed using T. fusca endoxylanases Xyn10B and Xyn11A and T. fusca cellulases, Cel48A exoglucanase and Cel5A endoglucanase. "
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