RNA aptamers were selected against an affinity column containing a farnesylated 
peptide modeled after the carboxyl terminus of K ras, the major oncogenic form 
of this small G protein family. After 10-rounds of selection, 25% of the RNA 
applied to the column could be specifically eluted. Sequence analysis of the 
binding RNA aptamers revealed two consensus sequences--GGGUGGG and GGGAGG. 
Quantitative fluorescence binding studies on two of the high-affinity aptamers, 
showed a binding affinities of 139 nM and 0.93 microM, respectively for the 
farnesylated peptide. Binding to the nonfarnesylated peptide was at least 
10-fold weaker, showing that the aptamers can recognize the hydrophobic farnesyl 
moiety. High affinity aptamers could be useful in specifically interfering with 
oncogenic ras function in particular, and G proteins in general.