Polymorphisms, Solvent Accessibility, and Evolutionary Conservation of Influenza A Virus PB1 Protein

ABSTRACT Protein polymorphisms, reflecting amino acid and nucleotide sequence divergence, provide insights into protein evolution. Here, we analyze sequence variation and structural features of influenza A virus (IAV) PB1 protein, an RNA-dependent RNA polymerase critical for viral replication. Our findings demonstrate that residue solvent accessibility strongly predicts polymorphism likelihood, with exposed sites exhibiting higher variability. Despite extensive polymorphism, we observe pervasive purifying selection across PB1, maintaining functional and structural constraints. These results highlight how protein architecture shapes evolutionary dynamics in viral proteins.