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Molecular Dynamics Study of Inorganic Surface Recognition by Engineered Proteins

Rosemary Braun*, a, Klaus Schultena, Dan Heidelb, Mehmet Sarikayab

aBeckman Institute, University of Illinois, Urbana-Champaign,
Urbana, IL 61801 USA

bUniversity of Washington, Seattle, WA

This is an abstract for a presentation given at the
Eighth Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is available on the web.

 

The biological control of inorganic crystal morphology is of interest to biologists studying hard tissue growth, bioengineers studying tissue engineering, and materials scientists working towards nanoscale control of crystal growth for functional materials. Sarikaya et al. have developed a genetic system to isolate proteins which control gold crystallization[1]. Such proteins may be utilized in the development of nanostructured materials for use in electronic and chemical applications. It was shown[2] that in the presence of gold binding protein (GBP) gold formed large, flat hexagonal crystals displaying the {111} plane. Such crystals were not seen to form in the presence of control proteins which do not bind to gold.

It is suggested that GBP binds preferentially to the {111} Au surface, and that the covering of the {111} face by the bound GBP plays a role in the mechanism by which GBP alters crystal morphology. Because the GBP sequence does not contain cysteine (known to form a covalent linkage with gold), the mechanism by which GBP adheres to gold is not obvious. It is also not readily apparent why the {111} surface would be preferred to, for example, the more sparsely populated {112} face. Both chemisorption (via GBP's methionine sulfurs) and physisorption (via polar side-chains) could play a role in the binding.

We have predicted structures for the three GBP sequences available using sequence similarity methods in addition to the Holley-Karplus prediction method. Of the three isolated GBPs, two are seen to have repeating motifs conducive to binding to a periodic surface. We present results of ab initio dynamics of the interaction between the GBP methionine side-chains and gold (the experimental literature is conflicting on whether the methionine sulfur is likely to form the bond). We also present results of molecular dynamics simulations of GBPs on both the {111} and {112} crystal surfaces, for both the case in which the methionine is bound and for which it is not, carried out to elucidate the mechanism by which the {111} surface is preferred.

Furthering the understanding of metal recognition by engineered proteins will facilitate a nanoscale tailoring of inorganic materials. The controlled assembly of inorganic materials using biological techniques has interesting implications for the development of materials with improved properties, the understanding of hard tissue growth, and the fabrication of molecular electronics[3].

References:
[1] Brown, S. Metal recognition by repeating polypeptides. Nature Biotechnology 15, 269-272 (1997).
[2] Brown, S., Sarikaya, M., and Johnson, E. A Genetic Analysis of Crystal Growth. J. Molecular Biology 299, 725-735 (2000).
[3] Sarikaya, M., Humbert, R., and Brown, S. Engineered proteins as recognition elements for nanomaterials assembly. Unpublished.


*Corresponding Address:
Rosemary Braun
Beckman Institute, University of Illinois, Urbana-Champaign
405 N Mathews
Urbana, IL 61801 USA
Email: braun@ks.uiuc.edu
Web: http://www.ks.uiuc.edu/Research/gbp/



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