Assignment of mutant tsN19 (complementation group E) of respiratory syncytial virus to the P protein gene

The mutation responsible for the temperature-sensitive (ts) phenotype of mutant tsN19 (complementation group E) of respiratory syncytial virus has been located to the P protein gene. Viral protein synthesis was completely restricted at 39 °C, and the tsN19 P protein did not react with an anti-P monoclonal antibody (MAb) (3–5) at 33 °C. Reversion of temperature sensitivity restored reactivity with MAb 3–5. Nucleotide sequence determination and in vitro expression of cDNA clones of P mRNA derived from wild-type, tsN19 and non-ts revertant-infected cells, revealed that temperature sensitivity and loss of reactivity with MAb 3–5 were consequences of a Gly → Ser amino acid change at position 172. A low M r polypeptide, which represented the C-terminal 93 amino acids of the P protein, was produced by internal initiation in the P open reading frame during in vitro translation, and a similar product was detected transiently in vivo.