HLA-A2 antigen phosphorylation in vitro by cyclic AMP-dependent protein kinase. Sites of phosphorylation and segmentation in class i major histocompatibility complex gene structure

• Published in: The Journal of biological chemistry Vol. 259; no. 21; pp. 13504 - 13510
• Main Authors: Guild, B C, Strominger, J L
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 10.11.1984; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Antigens; Biological and medical sciences; Cell Line; Fundamental and applied biological sciences. Psychology; Fundamental immunology; HLA Antigens - genetics; HLA-A2 Antigen; Humans; Lymphocytes - immunology; Macromolecular Substances; Major Histocompatibility Complex; Mice; Molecular immunology; Peptide Fragments - analysis; Phosphorus Radioisotopes; Phosphorylation; Phosphoserine - analysis; Protein Kinases - metabolism; Species Specificity; Human; Catalytic subunit; HLA-System; Genome organization; Phosphorylation; Enzyme; Major histocompatibility system; In vitro; Site specificity; Heavy-Peptide chain; Alloantigen; Exon; Protein kinase; Catalyst activity
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)90722-2

The heavy chain of the HLA-A2 antigen is phosphorylated by cyclic AMP-dependent protein kinase at two serine residues of the intracellular region. Limited proteolysis was performed on purified [32P]HLA-A2 antigens in order to define the sites of phosphorylation. Both of the phosphorylated serine residues are located in the carboxyl terminus of the heavy chain; one is encoded by exon 5, while the other is encoded by exon 6. The phosphoserine encoded by exon 5 is part of the conserved sequence Arg-Arg-Lys-Ser-Ser. This protein sequence contains the proper arrangement of amino acids for recognition and phosphorylation by the catalytic subunit of cyclic AMP-dependent protein kinase. In the murine class I antigens (H-2), exon 5 encodes a similar sequence of basic residues followed by one intervening residue and a threonine rather than a serine residue in the last amino acid position. A composite figure is presented that compares the carboxyl-terminal sequences of human and murine class I antigens and illustrates the known sites of phosphorylation recognized by various kinases. Each site of phosphorylation in the carboxyl terminus is contained within a conserved protein sequence encoded by one of the three exons. A separation and preservation of unique sites of phosphorylation could explain why there is segmentation in the genomic arrangement of class I molecules.