Aspen Tree Protein SP1 as a Biological Nanopore

Nanopores have been used as stochastic sensors for the detection of analytes that range from small molecules to DNA, RNA, and proteins. Proteins in a planar lipid bilayer platform can be used as nanopores in order to study and identify these biological analytes. In this approach, individual analyte molecules modulate the ionic current flowing through a single nanopore. SP1 (stable protein 1) is a ring-shaped, highly stable homododecamer protein, originally isolated from Aspen trees (P. euphratica). SP1 is stable under extreme conditions such as high temperatures, detergents and organic solvents, and over a wide range of pH. SP1 has a relatively large pore diameter (3-4 nm) which can be manipulated in order to specifically detect a variety of analytes (DNA, RNA, Proteins). It was recently shown that SP1 can be embedded into lipid bilayers, thus creating a nanopore. The protein can be modified in order to change the charge distribution on its surface to further increase its stability in the lipid bilayer; this can be done via site directed mutagenesis and/or chemical modifications to increase surface hydrophobicity.