Crystal structure of an avian influenza polymerase PA(N) reveals an endonuclease active site.

Abstract

The heterotrimeric influenza virus polymerase, containing the PA, PB1 and PB2 proteins, catalyses viral RNA replication and transcription in the nucleus of infected cells. PB1 holds the polymerase active site and reportedly harbours endonuclease activity, whereas PB2 is responsible for cap binding. The PA amino terminus is understood to be the major functional part of the PA protein and has been implicated in several roles, including endonuclease and protease activities as well as viral RNA/complementary RNA promoter binding. Here we report the 2.2 ångström (A) crystal structure of the N-terminal 197 residues of PA, termed PA(N), from an avian influenza H5N1 virus. The PA(N) structure has an alpha/beta architecture and reveals a bound magnesium ion coordinated by a motif similar to the (P)DX(N)(D/E)XK motif characteristic of many endonucleases. Structural comparisons and mutagenesis analysis of the motif identified in PA(N) provide further evidence that PA(N) holds an endonuclease active site. Furthermore, functional analysis with in vivo ribonucleoprotein reconstitution and direct in vitro endonuclease assays strongly suggest that PA(N) holds the endonuclease active site and has critical roles in endonuclease activity of the influenza virus polymerase, rather than PB1. The high conservation of this endonuclease active site among influenza strains indicates that PA(N) is an important target for the design of new anti-influenza therapeutics.

• Authors: Puwei Yuan, Mark Bartlam, Zhiyong Lou, Shoudeng Chen, Jie Zhou, Xiaojing He, Zongyang Lv, Ruowen Ge, Xuemei Li, Tao Deng, Ervin Fodor, Zihe Rao, Yingfang Liu
• Journal: Nature (Nature) Vol. 458 Issue 7240 Pg. 909-13 (Apr 16 2009) ISSN: 1476-4687 [Electronic] England
• PMID: 19194458 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• PA protein, influenza viruses
• Protein Subunits
• Viral Proteins
• RNA-Dependent RNA Polymerase
• Endonucleases

Topics

• Animals
• Birds (virology)
• Catalytic Domain
• Crystallography, X-Ray
• Endonucleases (chemistry, genetics, metabolism)
• Influenza A Virus, H5N1 Subtype (enzymology)
• Influenza in Birds (virology)
• Models, Molecular
• Protein Subunits (chemistry, genetics, metabolism)
• RNA-Dependent RNA Polymerase (chemistry, genetics, metabolism)
• Viral Proteins (chemistry, genetics, metabolism)