We introduced an RNA binding site for the amino acid tryptophan into RNAs that bind to phospholipid bilayer membranes. The resulting hybrid RNA (9:10Trp) still binds tryptophan with specificity and is also still able to bind phosphatidylcholine membranes as detected by gel filtration and FRET measurements between the intercalated green dye, YOYO-1 in RNA and Texas Red in membranes. RNA (9:10Trp) serves specifically to passively carry tryptophan across the membrane, without significant increase in general permeability. We previously found that membrane RNAs prefer the edges of lipid bilayer patches and other sites where irregular lipid conformations occur. This suggests that membrane RNAs should stabilize distorted lipid conformations, probably including those formed at transient transmembrane pores. These results show that a small-molecule-specific membrane carrier can be built of RNA, and suggest that other nanoconstructions in which RNA activities are brought to the membrane would be successful.

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