PB1 is the RNA-dependent RNA polymerase (RdRP) subunit, which carries out viral mRNA and genomic RNA synthesis in reactions with the cap-binding subunit PB2 and the endonuclease subunit PA. The influenza virus PB1 protein is the core subunit of the heterotrimeric polymerase complex (PA, PB1 and PB2) in which PB1 is responsible for catalyzing RNA polymerization and binding to the viral RNA promoter.
Polymerase basic 1 / PB1 cDNAs
There is no crystal structure available for PB1 protein except its N terminal 25 amino acids and C terminal about 80 amino acids. This is mainly due to its low solubility when expressed alone in bacteria or the low productivity of the active heterotrimeric polymerase complex when expressed in insect cells and mammalian cells.
PB1, the catalytic core and structural backbone of the polymerase, possesses four highly conserved amino acid motifs that are present among all viral RNA-dependent RNA polymerases. These four conserved motifs form a large functional domain with at least one 'invariant' amino acid per motif.
PB1 plays a central role in synthesis of influenza virus RNA genome, it has also become a promising target for developing new anti-influenza drugs. Mutations in the PB1 subunit of RNA-dependent RNA polymerase (RdRp) of influenza A virus can affect replication fidelity. Before the influenza A/H1N1 pandemic in 2009, most human influenza A/H1N1 viruses contained the avian-associated residue, serine, at position 216 in PB1. However, near the onset of the 2009 pandemic, human viruses began to acquire the mammalian-associated residue, glycine, at PB1–216, and PB1–216G became predominant in human viruses thereafter.
• Chunfeng Li.Integrating computational modeling and functional assays to decipher the structure-function relationship of influenza virus PB1 protein.SCIENTIFIC REPORTS.2014
• Giorgi Metrevelia.The origin of the PB1 segment of swine influenza A virus subtype H1N2 determines viral pathogenicity in mice.Virus Res. 2014
• Ruey-Wen Lin.Naturally occurring mutations in PB1 affect influenza A virus replication fidelity, virulence, and adaptability.Journal of Biomedical Science.2019
• Caroline Chu.Functional Analysis of Conserved Motifs in Influenza .Virus PB1 Protein.PLoS ONE.2012