Directed in vitro evolution of bacterial expansin BsEXLX1 for higher cellulose binding and its consequences for plant cell wall-loosening activities

Nathan K. Hepler, Daniel J. Cosgrove

Research output: Contribution to journalLetter

1 Citation (Scopus)

Abstract

Expansins are cell wall-loosening proteins found in all land plants and many microbial species. Despite homologous structures, bacterial expansins have much weaker cellulose binding and wall-loosening activity than plant expansins. We hypothesized stronger cellulose binding would result in greater wall-loosening activity and used in vitro evolution of Bacillus subtilis BsEXLX1 to test this hypothesis. Mutants with stronger binding generally had greater wall-loosening activity, but the relationship was nonlinear and plateaued at ~ 40% higher than wild-type. Mutant E191K exhibited stronger cellulose binding but failed to induce creep, evidently due to protein mistargeting. These results reveal the complexity of interactions between plant cell walls and wall-modifying proteins, an important consideration when engineering proteins for applications in biofuel production and plant pathogen resistance.

Original languageEnglish (US)
Pages (from-to)2545-2555
Number of pages11
JournalFEBS Letters
Volume593
Issue number18
DOIs
StatePublished - Sep 1 2019

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Plant Cells
Cellulose
Cell Wall
Embryophyta
Bacterial Structures
Protein Engineering
Proteins
Biofuels
Bacillus subtilis
Pathogens
Bacilli
Creep
Cells
In Vitro Techniques

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

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abstract = "Expansins are cell wall-loosening proteins found in all land plants and many microbial species. Despite homologous structures, bacterial expansins have much weaker cellulose binding and wall-loosening activity than plant expansins. We hypothesized stronger cellulose binding would result in greater wall-loosening activity and used in vitro evolution of Bacillus subtilis BsEXLX1 to test this hypothesis. Mutants with stronger binding generally had greater wall-loosening activity, but the relationship was nonlinear and plateaued at ~ 40{\%} higher than wild-type. Mutant E191K exhibited stronger cellulose binding but failed to induce creep, evidently due to protein mistargeting. These results reveal the complexity of interactions between plant cell walls and wall-modifying proteins, an important consideration when engineering proteins for applications in biofuel production and plant pathogen resistance.",
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AU - Cosgrove, Daniel J.

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AB - Expansins are cell wall-loosening proteins found in all land plants and many microbial species. Despite homologous structures, bacterial expansins have much weaker cellulose binding and wall-loosening activity than plant expansins. We hypothesized stronger cellulose binding would result in greater wall-loosening activity and used in vitro evolution of Bacillus subtilis BsEXLX1 to test this hypothesis. Mutants with stronger binding generally had greater wall-loosening activity, but the relationship was nonlinear and plateaued at ~ 40% higher than wild-type. Mutant E191K exhibited stronger cellulose binding but failed to induce creep, evidently due to protein mistargeting. These results reveal the complexity of interactions between plant cell walls and wall-modifying proteins, an important consideration when engineering proteins for applications in biofuel production and plant pathogen resistance.

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