Banta:BetaRoll

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{{Template:Banta_Lab}}
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[[Image:BetaRoll.jpg|thumb|400px|right|Crystal structure of a folded Beta Roll domain where the red spheres indicate the bound Ca+2 ions and the purple resides are randomized for molecular recognition (Dooley, Kim, Lu, Tu, and Banta, 2012 Biomacromolecules).]]
'''Evolving the Beta Roll Domain for Regulated Molecular Recognition'''  
'''Evolving the Beta Roll Domain for Regulated Molecular Recognition'''  
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Self-assembly is an essential process for all forms of lifeFor example, proteins spontaneously fold into well-defined 3-dimensional structures, and cellular organelles form that spatially segregate diverse cellular processesAs engineers aim to create  new devices and systems at ever decreasing size scales, self-assembly processes become increaseingly attactive techniques.
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Molecular recognition is ubiquitous in natureFrequently antibodies are used in technology applications where biomolecular recognition is to be employed, but antibodies have several limitations in these applications, including difficulty in easily removing bound targetsThis becomes especially important in the development of biosensors using electrochemical-based signal transduction schemes.
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We are collaborating with Plamen Atanassov at University of New Mexico, Scott Calabrese-Barton at Michigan State University and Shelley Minteer at Saint Louis University to make improved electrodes for biofuel cells.  In a biofuel cell, redox enzymes are immobilized on electrode surfaces.  Enzymes located at the anode are able to oxidize substrates and the electrons move through an external circuit to create power.  On the cathode, other redox enzymes are able to use the electrons to reduce oxygen to water.  The net result of this process is the generation of electricity from a variety of readily available biofuel sources, with oxygen as the terminal electron acceptor.
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Instead of trying to engineer allosteric control into a molecular recognition molecule, we have started with intrinsically disordered scaffold, the beta roll domain, and we are working to evolve this allosterically regulated scaffold for biomolecular recognition.  The naturally existing beta roll subdomain motif consists of tandem repeats of the sequence GGXGXDXUX, where U is an aliphatic amino acid and X is any amino acid. In the presence of calcium, the disordered peptide reversibly transitions to a beta roll spiral structure of two parallel beta sheet faces, where each beta strand has two solvent exposed variable residues.  
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The architecture of the electrodes is crucial for biofuel cell performance.  The enzymes on the electrodes must be positioned so that electrons can easily move between the enzymatic active site and the electorde surface (Direct Electron Transfer (DET)). Alternatively, the enzymes can be immoblilized with redox mediators, such as osmium, that facilitate the transport of electrons from the electrodes to the enzymes (Fig. 1).  In this Mediated Electron Transport (MET) configuration, the enzyme and mediators are immobilized in a polymer matrix on the electrode surface.  While this system has been used to demonstrate impressive biofuel cell performances, it is potentially hampered by poor dispersion of the enzyme and mediator within the polymer matrix, and complex manufacturing requirments.
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We are using biological self-assembly to improve the biofuel cell electrode construction and performance (Fig. 2).  Instead of combing enzymes and mediators in a polymer matrix, we are creating self-assembling protein-based hydrogels that intrinsically include the redox enzymes and the mediators.  In this configuration the loading of the enzyme and the mediators into the hydrogel can be finely controlled, and the hydrogel assembly process will be well-defined and repeatable.  These new bioelectrocatalytic hydrogels will have the potential to significantly improve biofuel cell performance.
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We have characterized a native beta roll subdomain with various end-capping groups in order to identify a minimal calcium-responsive beta roll unit. We believe that the beta roll faces are suitable binding surfaces and that calcium-induced structure formation can be used as a mechanism to control the formation of the engineered biomolecular recognition interface. The reversibility of the calcium binding suggests that the engineered biomolecular recognition will likewise be reversibly controllable. We have randomized one face of this minimal beta roll unit and we are using directed evolution to identify beta roll peptides with biomolecular recognition capabilities.
   
   
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<biblio>
<biblio>
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#Paper5 pmid=21416544
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#Paper4 pmid=20438736
#Paper3 pmid=19860484
#Paper3 pmid=19860484
#Paper2 pmid=17376876
#Paper2 pmid=17376876
#Paper1 pmid=17450770
#Paper1 pmid=17450770
</biblio>
</biblio>

Revision as of 14:33, 8 October 2012

Crystal structure of a folded Beta Roll domain where the red spheres indicate the bound Ca+2 ions and the purple resides are randomized for molecular recognition (Dooley, Kim, Lu, Tu, and Banta, 2012 Biomacromolecules).
Crystal structure of a folded Beta Roll domain where the red spheres indicate the bound Ca+2 ions and the purple resides are randomized for molecular recognition (Dooley, Kim, Lu, Tu, and Banta, 2012 Biomacromolecules).

Evolving the Beta Roll Domain for Regulated Molecular Recognition

Molecular recognition is ubiquitous in nature. Frequently antibodies are used in technology applications where biomolecular recognition is to be employed, but antibodies have several limitations in these applications, including difficulty in easily removing bound targets. This becomes especially important in the development of biosensors using electrochemical-based signal transduction schemes.

Instead of trying to engineer allosteric control into a molecular recognition molecule, we have started with intrinsically disordered scaffold, the beta roll domain, and we are working to evolve this allosterically regulated scaffold for biomolecular recognition. The naturally existing beta roll subdomain motif consists of tandem repeats of the sequence GGXGXDXUX, where U is an aliphatic amino acid and X is any amino acid. In the presence of calcium, the disordered peptide reversibly transitions to a beta roll spiral structure of two parallel beta sheet faces, where each beta strand has two solvent exposed variable residues.

We have characterized a native beta roll subdomain with various end-capping groups in order to identify a minimal calcium-responsive beta roll unit. We believe that the beta roll faces are suitable binding surfaces and that calcium-induced structure formation can be used as a mechanism to control the formation of the engineered biomolecular recognition interface. The reversibility of the calcium binding suggests that the engineered biomolecular recognition will likewise be reversibly controllable. We have randomized one face of this minimal beta roll unit and we are using directed evolution to identify beta roll peptides with biomolecular recognition capabilities.


Related Publications

  1. Shur O, Wu J, Cropek DM, and Banta S. . pmid:21416544. PubMed HubMed [Paper5]
  2. Blenner MA, Shur O, Szilvay GR, Cropek DM, and Banta S. . pmid:20438736. PubMed HubMed [Paper4]
  3. Szilvay GR, Blenner MA, Shur O, Cropek DM, and Banta S. . pmid:19860484. PubMed HubMed [Paper3]
  4. Chockalingam K, Blenner M, and Banta S. . pmid:17376876. PubMed HubMed [Paper2]
  5. Banta S, Megeed Z, Casali M, Rege K, and Yarmush ML. . pmid:17450770. PubMed HubMed [Paper1]
All Medline abstracts: PubMed HubMed
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