Recently, many molecular modeling methods are being developed to better understand the principles underlying protein folding. In the present study, fully flexible dinucleotides d(pApA), d(pApC), d(pApG), d(pApT), d(pCpA), d(pCpC), d(pCpG), d(pCpT), d(pGpA), d(pGpC), d(pGpG), d(pGpT), d(pTpA), d(pTpC), d(pTpG) and d(pTpT) were docked onto the surface of p21-activated kinase 4 (PAK4) kinase domain. The results showed that automated docking was a useful tool to identify the functional sites of PAK4 and it may provide a theoretical basis for the interaction data obtained from previous experiments. Therefore, structure-based docking with fully flexible dinucleotide probes might be a good tool to predict and annotate the functional sites of enzymes.