RNA has been found to be more important than the mere intermediate of the information flow between DNA to protein. In the so called RNA "world" [1], RNA has been accepted as an earlier hierarchy material than DNA. If the "RNA world" really exists, the function of RNA-binding proteins in those very ancient living form are critical, because those proteins have directly regulate the life process and lead it into current evolution stage. An RNA transcript interacts with many different RNA-binding proteins from transcription to translation [2].
Pyrococcus furiosus (P. furiosus) is an ancient thermophilic microbe with a genome size of only about 2 Mb[3]. Its small genome size and the thermophilic property allow the easy construction of a protein expression library in vitro. In previous work, we have constructed an in vitro protein expression library of such an ancient hyperthermophilic archaeon [4]. In this work, we designed a multi-structure RNA oligo with 27 nucleotides (MPOR-27). Using this oligo RNA, we screened the entire P. furiosus in vitro expression protein pool. Here we show that protein pool 658, which has a strong RNA-binding activity, may contain a novel RNA-binding protein. The PF1684 protein from the P.furiosus genome exhibits this RNA-binding activity.