RT Journal Article SR Electronic(1) A1 Byrappa, Sridhar A1 Gupta, Kailash C.YR 1999 T1 Human parainfluenza virus type 1 phosphoprotein is constitutively phosphorylated at Ser-120 and Ser-184 JF Journal of General Virology, VO 80 IS 5 SP 1199 OP 1209 DO https://doi.org/10.1099/0022-1317-80-5-1199 PB Microbiology Society, SN 1465-2099, AB RNA-dependent RNA polymerases of single-stranded, negative-sense RNA viruses comprise a phosphoprotein (P) and a large protein. The constitutive phosphorylation of the P protein in these viruses is highly conserved, yet the functional significance of phosphorylation is enigmatic. To approach this problem, phosphorylation sites were determined in two closely related paramyxovirus P proteins. Sendai virus (SV) is a prototypic paramyxovirus. Previously, using a phosphopeptide mapping technique, the primary constitutive phosphorylation site of SV P protein was mapped to Ser-249. Phosphorylation at Ser-249 is dependent on the presence of Pro-250. Human parainfluenza virus type 1 (HPIV-1) P protein has 66% similarity to SV P protein and its predicted secondary structure is highly similar to that of SV P protein. However, there is no obvious conserved phosphorylation site in HPIV-1 P protein. Using the phosphopeptide mapping strategy, the constitutive phosphorylation sites of HPIV-1 P protein were mapped. The HPIV-1 P protein is primarily phosphorylated at Ser-120. Phosphorylation at Ser-120 is dependent on the presence of Pro-121. It also has a minor phosphorylation site at Ser-184. The sequence at Ser-184 does not match any consensus phosphorylation target site for the known kinases. Significantly, the P proteins from both viruses are constitutively and primarily phosphorylated at one serine and the phosphorylation of that serine is dependent on the presence of a proline on its carboxyl side., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-80-5-1199