Aichi virus is a single stranded plus RNA (+ RNA) virus which causes gastroenteritis in humans. Aichi virus is also used as a model organism for studying related more virulent viruses like SARS, HCV, West Nile virus, Yellow fever virus etc. Protein 3Dpol, RNA dependent RNA polymerase, is a key enzyme for the life cycle of a + RNA viruses. The 3Dpol enzymes catalyze formation of phosphodiester bond between RNA nucleotides. The picornaviral RNA replication is protein 3Dpol activity dependent. The RNA replication is curtail for both viral genome multiplication and viral protein translation.
+ RNA viruses hijack phosphatidylinositol 4-kinases (PI4Ks) to generate membranes highly enriched in phosphatidylinositol 4-phosphate (PI4P). These viral induced membrane structures serves as structural scaffold for RNA replication and also to protect from innate intracellular immunity. We studied interaction of 3Dpol with PI4P lipid using recombinant 3Dpol from Aichi virus 1 (AiV), Poliovirus 1 (PV), Coxsackievirus b3 (CV) and Enterovirus 71 (EV). The polymerase activities of 3Dpol enzymes were compared by PETE fluorescence assay [1].
We also determined the crystal structure of Aichi 3Dpol at 3.8 Å resolution. The structure revealed an overall conserved fold. However, the Aichi 3Dpol has a different N-terminal structure compared to other related picornaviruses (PV, CV, EV), where the N-terminal residue is buried in a pocket at the base of fingers domain. Our structure reveals that Aichi 3Dpol can not stabilize itself by a slip of its first redue in the hydrophobic core of the protein.