PtSIT1: Protein Function in Silicic Acid Transport for Biomimetic Silica Synthesis

Undergraduate #139
Discipline: Chemistry and Chemical Sciences
Subcategory: Biochemistry (not Cell and Molecular Biology and Genetics)

Brenna Kirk - New College of Florida
Co-Author(s): Paul Curnow and Laura Senior, University of Bristol, Bristol, England Terence A. Nile, University of North Carolina at Greensboro

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Diatoms are eukaryotic algae that mineralize an external cell wall composed of hydrated silica. This process requires diatoms to uptake soluble silicon (silicic acid) from the surrounding environment by specific silicic acid transport proteins (SITs). This family of proteins is relatively uncharacterized. The goal of this project was to 1) express and purify SIT1 from the diatom Phaeodactylum tricornutum (PtSIT1), 2) reconstitute the protein into a synthetic lipid vesicle and to 3) determine whether SIT1 can behave as a silicic acid transporter in vivo for eventual applications in nanotechnology. PtSIT1 was overexpressed in yeast and purified in the solubilizing detergent Fos-choline 12. The purified protein was successfully reconstituted into synthetic liposomes and silicic acid uptake was assessed using a fluorescent assay which used zinc silicate fluorescence. This method also was used to determine that silicic acid transported by PtSIT1 displayed Michaelis-Menten kinetics with a Km of 1.48 μM. Preliminary electron microscopy suggested that the silicic acid silicic acid transported into the liposome condense to form silica nanoparticles in the presence of tetraethylenepentamine, a condensing agent. This work confirms that PtSIT1 can be utilized in further exploration of biomineralization of silica in vivo in an effort to explore ‘green’ syntheses of silica nanoparticles.

Funder Acknowledgement(s): Funding for this research came from the National Science Foundation, grant number 1262847.

Faculty Advisor: Steven Shipman,