An RNA aptamer that discriminates bovine factor IX from human factor IX

An RNA aptamer has been selected by SELEX against bovine factor IX using an RNA pool containing 74-nucleotides randomized region. Selected RNA aptamer (Clone 5) could discriminate bovine factor IX effectively from human factor IX. Interestingly, the nucleotide regions 73-78 and 80-83 of the selected aptamer were determined to be important for bovine factor EK-binding using phosphate interference. Based on phosphate interference and binding studies the minimal motif for aptamer with discriminating ability is found with the nucleotide regions from 65 to106. The discriminating ability of this mini aptamer is calculated as more than 1,000 fold. The equilibrium dissociation constant (K-d) for the above complex was 10 nM as determined by surface plasmon resonance. Based on the available structural informations, probable binding site of aptamer on the target was predicted.