A Structure-Function Diversity Survey of the RNA-Dependent RNA Polymerases From the Positive-Strand RNA Viruses

Jia, Hengxia; Gong, Peng

A large number of RdRPs from the positive-strand RNA viruses are proteolytic products of viral polyproteins (Palmenberg, 1990; Wimmer and Nomoto, 1993; Reed and Rice, 2000; Bartenschlager et al., 2010; Pietila et al., 2017) . Since not all related proteolytic cleavage sites have been reported for some of the virus families, we were only able to define N-and C-terminal boundaries for 33 RdRPs among the 49 representatives (Figure 1 and Table 1) . For the rest of the RdRPs, 7 of them only have a defined C-terminus, and 9 of them have both termini undefined based on our best knowledge. Hence, functional studies to identify polyprotein proteolytic sites are necessary to improve the global picture RdRP primary structure diversity, and our analyses are based on incomplete boundary assignments. The overall size of the RdRPs with clear boundaries ranges from ∼460 to ∼1930 residues, indicating that the primary structure of these RdRPs are quite diverse and potential functional regions are likely integrated into some of these RdRP proteins.