title: Characterization of the phosphorylation status of the hepatitis B virus X-associated protein 2.
abstract: The cytosolic Ah receptor (AhR) heterocomplex consists of one molecule of the AhR, a 90-kDa heat shock protein (Hsp90) dimer, and one molecule of the hepatitis B virus X-associated protein 2 (XAP2). Serine residues 43,53,131-2, and 329 on XAP2-FLAG were identified as putative phosphorylation sites using site-directed mutagenesis followed by two-dimensional phosphopeptide mapping analysis. Protein kinase CK2 (CK2) was identified as the 45-kDa kinase from COS 1 cell or liver extracts that was responsible for phosphorylation of serine 43 in the XAP2 peptide 39-57. Loss of phosphorylation at any or all of the serine residues did not significantly affect the ability of XAP2-FLAG to bind to the murine AhR in rabbit reticulocyte lysate or Hsp90 in COS-1 cells. Furthermore, all of these serine mutants were able to sequester murine AhR-YFP into the cytoplasm as well as wild-type XAP2. YFP-XAP2 S53A was unable to enter the nucleus, indicating a potential role of phosphorylation in nuclear translocation of XAP2.
mesh_terms: D000409:Alanine; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006515:Hepatitis B virus / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine; D014162:Transfection
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D010748:Phosphopeptides; D011506:Proteins; D011993:Recombinant Fusion Proteins; C103265:aryl hydrocarbon receptor-interacting protein; D012694:Serine; D000409:Alanine