Genes 1 and 2 of pneumonia virus of mice encode proteins which have little homology with the 1C and 1B proteins of human respiratory syncytial virus.

Genes 1 and 2 of pneumonia virus of mice (PVM) consist of 410 and 571 nucleotides and encode proteins of 113 and 156 amino acids respectively. The proteins show no extensive (gene 1 analogous to 1C) or low (gene 2 analogous to 1B) homology to their presumed counterparts in human respiratory syncytial virus (HRSV). The strongest homology is between regions of approximately 35 amino acids located near the carboxy termini of the gene 2 product and the 1B protein with 29% identity, although a lower level of homology can be detected throughout much of these proteins (18% identity overall). These observations contrast with the conservation of 1C and 1B proteins between subgroups of HRSV and with the conservation of nucleocapsid proteins between HRSV and PVM.