Purification and characterization of MAR1. A mitochondrial associated ribonuclease from Leishmania tarentolae

A relatively thermostable 22-kDa endoribonuclease (MAR1) was purified more than 10,000-fold from a mitochondrial extract of Leishmania tarentolae and the gene cloned. The purified nuclease has a Km of 100-145 +/- 33 nM and a Vmax of 1.8-2.9 +/- 2 nmol/min, depending on the RNA substrate, and yields a 3'-OH and a 5'-phosphate. Cleavage was limited to several specific sites in the substrate RNAs tested, but cleavage of pre-edited RNAs was generally independent of the addition of cognate guide RNA. The MAR1 gene was expressed in Escherichia coli or in L. tarentolae cells, and the recombinant protein was affinity-purified. The cleavage specificity of the recombinant enzyme from L. tarentolae was identical to that of the native enzyme. The single copy MAR1 gene maps to an 820-kilobase pair chromosome and contains an open reading frame of 579 nucleotides. The 18-amino acid N-terminal sequence shows characteristics of an uncleaved mitochondrial targeting sequence. Data base searching revealed two homologues of MAR1 corresponding to unidentified open reading frames in Caenorhabditis elegans (GenBankTM accession number Z69637) and Archaeoglobus fulgidus (GenBankTM accession number AE000943). The function of MAR1 in mitochondrial RNA metabolism in L. tarentolae remains to be determined.     

Operating experience with lubricating oils in diesel locomotive engine

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 10, pp. 21–22, October, 1988.     

Expression of E-selectin, sialyl Lewis X, and macrophage inflammatory protein-1alpha by colonic epithelial cells in ulcerative colitis

The pathogenic significance of cell adhesion molecules (CAMs) in ulcerative colitis (UC) is largely unknown. Colonic expression of E-selectin, sialyl Lewis X (sLe(x)), and macrophage inflammatory protein-1x (MIP-1alpha) as well as serum concentrations of E-selectin and MIP-1alpha in UC were studied. Thirty patients with UC, 10 patients with irritable bowel syndrome, and 10 healthy subjects were included. Colonic biopsies were stained immunohistochemically, and blood concentrations were measured with an ELISA technique. Soluble E-selectin did not correlate with diagnosis or disease activity. MIP-1alpha was below the detection limit. Epithelial cells expressed all three molecules, both on surface membranes and intracellularly. sLe(x) staining was weaker (P = 0.0002) and MIP-1alpha staining stronger (P = 0.014) in UC patients than in controls. Leukocyte MIP-alpha staining correlated with diagnosis (P = 0.021), sLe(x) staining (P = 0.023), and colonoscopy (P = 0.018). It is shown that E-selectin, sLe(x), and MIP-1alpha are synthesized and expressed by epithelial cells, indicating that CAMs are not only involved in leukocyte extravasation and migration, but also in the interaction between leukocytes and colonic epithelium. This knowledge might contribute to the development of improved treatments in UC.     

Human monocyte-derived macrophages express an approximately 120-kD Ox-LDL binding protein with strong identity to CD68

A protein that specifically binds oxidized LDL (Ox-LDL) has recently been characterized in mouse peritoneal macrophages and identified as macrosialin, a protein with a molecular weight of 95 kD. First, the present work shows that human monocyte-derived macrophages express a membrane protein with a molecular weight of approximately 120 kD that selectively binds Ox-LDL. Second, we tested whether this approximately 120-kD Ox-LDL binding protein had any relation to CD68, the human homologue of macrosialin. The following evidence was obtained to support the role of CD68 as an Ox-LDL binding protein: (1) Ligand blots with Ox-LDL and Western blots with Ki-M6, an anti-human CD68 monoclonal antibody, revealed a single band with a molecular weight of approximately 120 kD under reducing and nonreducing condition. (2) The expression patterns of the approximately 120-kD Ox-LDL binding membrane protein and of CD68 paralleled each other during monocyte/macrophage differentiation. (3) Digestion with N-glycosidase F demonstrated that both CD68 and the Ox-LDL binding protein are glycoproteins; both showed a similar shift of approximately 18 kD in apparent molecular weight. (4) CD68, probed with monoclonal antibody Ki-M6, and the approximately 120-kD Ox-LDL binding protein were coprecipitated with EMB11, another anti-CD68 antibody. About 5000 molecules of CD68 are expressed on the cell surface of human macrophages. Ligation of 125I-Ki-M6 to cells leads to its internalization and degradation. This capacity would be sufficient to allow for the specific uptake and degradation of Ox-LDL. Taken together, these data support a role for CD68 as a specific Ox-LDL binding protein in human monocyte-derived macrophages.