title: Met-ase: cloning and distinct chromosomal location of a serine protease preferentially expressed in human natural killer cells.
abstract: A cDNA clone encoding a human NK serine protease was obtained by screening a lambda-gt10 library from the Lopez NK leukemia with the rat natural killer Met-ase (RNK-Met-1) cDNA clone. In Northern blot analysis human Met-ase (Hu-Met-1) cDNA hybridized with a 0.9-kb mRNA in two human NK leukemia cell lines, unstimulated human PBMC, and untreated purified CD3-CD56+ large granular lymphocytes. Unlike other members of the granzyme family that are highly expressed in activated peripheral T cells, the Hu-Met-1 transcript was barely detected in a population of PMA and ionomycin or IL-2-treated high density T cells. Several in vitro cultured Burkitt lymphomas, chronic- and promyeloid leukemias, acute lymphoblastic leukemias, and colon and ovarian carcinomas and colon and ovarian carcinomas did not express Hu-Met-1 mRNA. Hu-Met-1 mRNA expression in a small number of human T cell tumor lines did not correlate with any particular phenotype or stage of development. The presence of Hu-Met-1 mRNA closely correlated with the Met-ase activity of cellular lysates prepared from these various human peripheral blood subsets and in vitro cultured cell lines. Met-ase activity detected in whole cell lysates of cytotoxic lymphocytes was associated with the cytoplasmic granules of these cells. The nucleotide sequence of the Hu-Met-1 cDNA clone encodes a predicted serine protease of 257 amino acids. The predicted protein is an active enzyme of 232 amino acids with a calculated unglycosylated m.w. of 27,100. Hu-Met-1 is 66% identical to RNK-Met-1 at the amino acid level. The human and rat mature protein sequences conserve the active site His, Asp, and Ser amino acids that form the catalytic triad of serine proteases, all 8 cysteine residues, and several amino acids critical in the formation of the substrate binding pocket. The gene for the Hu-Met-1 serine protease is located on chromosome 19, which distinguishes it from any other member of the human granzyme family.
authors.affiliation: Cellular Cytotoxicity Laboratory, Austin Research Institute, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Smyth
authors.forename: T J
authors.initials: TJ
authors.lastname: Sayers
authors.forename: T
authors.initials: T
authors.lastname: Wiltrout
authors.forename: J C
authors.initials: JC
authors.lastname: Powers
authors.forename: J A
authors.initials: JA
authors.lastname: Trapani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D002888:Chromosomes, Human, Pair 19; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000302:isolation & purification; D006801:Humans; D007694:Killer Cells, Natural / Q000201:enzymology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; C084504:Hu-Met-1; D012697:Serine Endopeptidases