Structural basis of the influenza A virus RNA polymerase PB2 RNA-binding domain containing the pathogenicity-determinant lysine 627 residue.


Because the influenza A virus has an RNA genome, its RNA-dependent RNA polymerase, comprising the PA, PB1, and PB2 subunits, is essential for viral transcription and replication. The binding of RNA primers/promoters to the polymerases is an initiation step in viral transcription. In our current study, we reveal the 2.7 A tertiary structure of the C-terminal RNA-binding domain of PB2 by x-ray crystallography. This domain incorporates lysine 627 of PB2, and this residue is associated with the high pathogenicity and host range restriction of influenza A virus. We found from our current analyses that this lysine is located in a unique "phi"-shaped structure consisting of a helix and an encircled loop within the PB2 domain. By electrostatic analysis, we identified a highly basic groove along with this phi loop and found that lysine 627 is located in the phi loop. A PB2 domain mutant in which glutamic acid is substituted at position 627 shows significantly lower RNA binding activity. This is the first report to show a relationship between RNA binding activity and the pathogenicity-determinant lysine 627. Using the Matras program for protein three-dimensional structural comparisons, we further found that the helix bundles in the PB2 domain are similar to that of activator 1, the 40-kDa subunit of DNA replication clamp loader (replication factor C), which is also an RNA-binding protein. This suggests a functional and structural relationship between the RNA-binding mechanisms underlying both influenza A viral transcription and cellular DNA replication. Our present results thus provide important new information for developing novel drugs that target the primer/promoter RNA binding of viral RNA polymerases.

DOI: 10.1074/jbc.C800224200

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@article{Kuzuhara2009StructuralBO, title={Structural basis of the influenza A virus RNA polymerase PB2 RNA-binding domain containing the pathogenicity-determinant lysine 627 residue.}, author={Takashi Kuzuhara and Daisuke Kise and Hiroko Yoshida and Takahiro Horita and Yoshimi Murazaki and Akie Nishimura and Noriko Echigo and Hiroko Utsunomiya and Hideaki Tsuge}, journal={The Journal of biological chemistry}, year={2009}, volume={284 11}, pages={6855-60} }