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: [email protected]
Web: http://www.ks.uiuc.edu/Research/gbp/
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