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Recombinatorial and Predictive Methods to Increase Cellulase Thermostability and Structural Analysis of a Thermostable P450


Komor, Russell Scott (2012) Recombinatorial and Predictive Methods to Increase Cellulase Thermostability and Structural Analysis of a Thermostable P450. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/A1ZX-3W42.


To address the world’s need for improved biomass breakdown for the production of renewable fuel, we sought to improve cellulase thermostability and thereby enzyme lifetime, operating temperature, and specific activity. We created an eight block SCHEMA recombination library based on five fungal cellobiohydrolase class I (CBHI) enzymes. By characterizing this library, we identified several stabilizing sequence blocks and combined these to produce a set of well-expressed, thermostable CBHI chimeras. To further increase the stability of these chimeras, we used a combination of the chimera thermostability screening data, a consensus analysis of 40 naturally occurring CBHI sequences, and FoldX ΔΔG predictions to identify individual mutations for testing. Our final enzyme has a T50 9.3 °C greater than that of the most stable parental CBHI, resulting in a 10 °C increase in optimal temperature and a 50% increase in total sugar production at the optimal temperature.

To produce an ideal parent for directed evolution for improved activity on varied compounds, we increased the thermostability of a P450BM3 enzyme with broad substrate specificity to produce enzyme 9-10ATS. Directed evolution libraries based on 9-10ATS produced variants with improved activity on a number of structurally diverse compounds. We determined the structure of 9-10ATS using x-ray crystallography and compared it to other P450BM3 structures. Examination of the stucture shows clear structural basis for the thermostabilizing mutations and broad substrate specificity.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Protein Engineering; Recombination; Structural Biology; Directed Evolution; Cellulase; P450; Protein Thermostability
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Arnold, Frances Hamilton
Thesis Committee:
  • Arnold, Frances Hamilton (chair)
  • Tirrell, David A.
  • Mayo, Stephen L.
  • Gray, Harry B.
Defense Date:14 December 2011
Record Number:CaltechTHESIS:12212011-144253704
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6757
Deposited By: Russell Komor
Deposited On:26 Jan 2012 23:36
Last Modified:08 Nov 2023 00:11

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