title: Site-directed mutagenesis of the avian retrovirus nucleocapsid protein, pp 12, at Serine 40, the primary site of phosphorylation in vivo.
abstract: The major nucleocapsid protein of avian retroviruses, pp 12, binds to single-stranded viral RNA with high affinity. Phosphorylation at Ser-40 is necessary for this binding. In order to examine the role of phosphorylation of serine 40 in the biological function of pp 12, we have introduced a series of amino acid substitutions at this position in the Rous sarcoma virus (Pr-C) protein. Substitution of threonine, alanine, or three other amino acids for Ser-40 had very little or no detectable effect on viral replication, nor did the control substitution of glycine for Ser-43, a nonphosphorylated residue. In vivo and in vitro, the Ala-40 and probably the Thr-40 substituted p 12 proteins are phosphorylated at alternative sites which are phosphorylated to a minor extent in vivo in the wild type protein. A study of the RNA binding properties of Ala-40 substituted p 12 has indicated that the protein has been stabilized in a high affinity RNA binding state which is independent of phosphorylation. The viability of the Ala-40 mutant virus indicates that this high binding affinity may be required for biological activity.
mesh_terms: D000595:Amino Acid Sequence; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D002213:Capsid / Q000235:genetics*; D036022:Capsid Proteins; D002851:Chromatography, High Pressure Liquid; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010957:Plasmids; D012313:RNA / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism; D012191:Retroviridae Proteins; D012694:Serine; D013329:Structure-Activity Relationship; D014758:Viral Core Proteins / Q000235:genetics*; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; D012367:RNA, Viral; D012191:Retroviridae Proteins; D014758:Viral Core Proteins; C054897:nucleocapsid protein, Avian retrovirus; D012694:Serine; D012313:RNA; D012194:RNA-Directed DNA Polymerase