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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated cytoplasmic membranes from Micrococcus lysodeikticus were able to incorporate [14C]mannose from GDP-[14C]mannose. Labelled mannose remained in the membrane fraction after its repeated washing and lipid extraction. Sodium dodecyl sulfate gel electrophoresis in 12% acrylamide showed a set of bands with molecular weights ranging from 230 000 to 19 000 which stained for protein and carbohydrate, and incorporated [14C]mannose. Some of these bands reacted with different lectins (concanavalin A, wheat germ agglutinin and ricin). Furthermore, the mannose was incorporated via a glycosylation pathway similar to that followed in eukaryotic system as shown by the preliminary identification of a lipid intermediate transferring the sugar to proteins and by the differential sensitivity to bacitracin and tunicamycin. These complex membrane components were sensitive to digestion with pronase. All the results presented suggest their glycoprotein nature.
Mol Cell Biochem 1986 Feb
PMID:Mannose incorporation and lectin recognition of pronase-sensitive components in Micrococcus lysodeikticus (M. luteus) membranes. 375 4

The toxic subunit of a plant ricin has been conjugate by a disulfide bond to a polyclonal rabbit antibody specific for the L-chain of human IgG. Both the antibody and ricin A-chain retained their original biological activity after conjugation. This conjugate proved to be a potent cytotoxin for surface Ig positive Burkitt lymphoma EB-3 cells, growing in vitro and produced 50% inhibition of protein synthesis at level of 1.4 x 10(-9) M. When tested for cytotoxic action on target cells, the composite conjugate molecule was at least 100 times more effective than antibodies alone, ricin A-chain alone or a conjugate ricin A-chain--normal rabbit IgG.
Mol Biol (Mosk)
PMID:[Selective cytotoxicity of an antibody-ricin A chain conjugate for human tumor cells]. 404 33

We have previously reported the isolation and characterization of Chinese hamster ovary (CHO) cell mutants defective in the internalization of ricin (Ray, B., and Wu, H.C. (1982) Mol. Cell. Biol. 2, 535-544). These mutants also do not exhibit the enhancement of ricin internalization by nigericin pretreatment at a low concentration, which is observed in the wild-type CHO cells. An analysis of somatic cell hybrids between the mutant and the toxin-sensitive wild-type CHO cell line shows that all of the phenotypes associated with the toxin resistance mutation are dominant in the hybrid cell lines. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [3H]palmitic acid-labeled cell extracts from the mutant and toxin-resistant hybrid cell lines has revealed an increased incorporation of [3H] palmitic acid into two proteins with apparent molecular weights near 30,000 in the mutant and hybrid cells as compared to that in the wild-type cell line. Our studies indicate that these two fatty acyl proteins might be related to a dominant mutation(s) which results in a decreased uptake of ricin.
 ...
PMID:Genetic and biochemical analysis of mutation(s) affecting ricin internalization in Chinese hamster ovary cells. 649 Jun 39

By osmotic lysis of pinocytic vesicles we were able to inject ricin or ricin A chain directly into the cytosol of Chinese hamster ovary cells. The lag time of 1 to 2 h before the onset of the inhibition of protein synthesis by ricin in intact cells was reduced to 15 to 30 min by this method. Preincubation of cells with a low concentration of nigericin, which was shown earlier to enhance the cytotoxicity of ricin, had no effect under this condition. Direct transfer of either intact ricin or the ricin A subunit by osmotic lysis of pinocytic vesicles into the cytosol of the ricin-resistant CHO mutant cell line 4-10 rendered the mutant 4-10 cells as sensitive to ricin as the CHO pro wild-type cells. Both the lag time and the rate of inhibition of protein synthesis in the wild-type and mutant cell lines after the introduction of ricin by osmotic lysis of pinocytic vesicles were the same. These results indicate that injection of ricin into the cytosol by osmotic lysis of pinosomes bypasses the internalization defect in the mutant cell line.
Mol Cell Biol 1984 Jul
PMID:Osmotically induced microinjection of ricin bypasses a ricin internalization defect in a Chinese hamster ovary mutant cell line. 650 48

Chinese hamster ovary mutants simultaneously resistant to ricin and Pseudomonas toxin have been isolated. Two mutant cell lines (4-10 and 11-2) were found to retain normal levels of binding of both ricin and Pseudomonas toxin. They were defective in the internalization of [125I]ricin into the mutant cells, as measured by both a biochemical assay for ricin internalization and electron microscopic autoradiographic studies. Although pretreatment of Chinese hamster ovary cells with a Na+/K+ ionophore, nigericin, resulted in an enhancement of the cytotoxicities of ricin and Pseudomonas toxin in the wild-type Chinese hamster ovary cells, preculture of the mutant cells did not alter the susceptibility of the mutant cells to either toxin. These results provide further evidence that there is a common step in the internalization process for ricin and Pseudomonas toxin.
Mol Cell Biol 1982 May
PMID:Chinese hamster ovary cell mutants defective in the internalization of ricin. 681 98

Internalization of ricin into Chinese hamster ovary cells has been investigated. Combined treatment with galactose and pronase at 0 degrees C resulted in a complete release of surface-bound [125I]ricin into the media. Galactose-pronase-resistant cell-bound [125I]ricin represents internalized ricin molecules inside the cells. The internalization process is time, temperature, and concentration dependent. The pH optimum of internalization of ricin is about pH 7. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis has revealed that intact ricin molecules are internalized. Neither reduction nor proteolytic processing of ricin is required for the entry of ricin into Chinese hamster ovary cells.
Mol Cell Biol 1981 Jun
PMID:Internalization of ricin in Chinese hamster ovary cells. 696 7

Nigericin and monensin, ionophores for Na+ and K+, have been found to enhance the cytotoxicities of abrin, ricin, and Pseudomonas aeruginosa exotoxin A in Chinese hamster ovary (CHO) cells. They do not affect the cytotoxicity of diphtheria toxin in the same cell line. Maximal sensitization of the CHO cells toward ricin and Pseudomonas toxin requires preculture of CHO cells in the presence of nigericin. Inhibition of protein synthesis in CHO cells by ricin or Pseudomonas toxin is also enhanced by preculture of CHO cells in the presence of nigericin. These results suggest a common step in the intoxication process of ricin and Pseudomonas toxin, the rate of which is facilitated by pretreatment with nigericin. This step is, however, not shared by the intoxication of CHO cells with diphtheria toxin.
Mol Cell Biol 1981 Jun
PMID:Enhancement of cytotoxicities of ricin and Pseudomonas toxin in Chinese hamster ovary cells by nigericin. 696 8

Biochemical and electron microscopic autoradiographic studies with [125I] ricin have revealed that nigericin-pretreated Chinese hamster ovary cells are more efficient than untreated cells in the internalization of the toxin into the cells. These results suggest that the enhanced rate of internalization of ricin in nigericin-pretreated cells may account for the enhancement of cytotoxicity of ricin in Chinese hamster ovary cells by nigericin.
Mol Cell Biol 1981 Jun
PMID:Enhanced internalization of ricin in nigericin-pretreated Chinese hamster ovary cells. 696 9

Treatment prior to infection with Trypanosoma cruzi trypomastigotes of Vero, MA-103, and chick muscle cells with concanavalin A, phytohemagglutinin, wheat germ agglutinin and ricin I results in a diminished parasite interiorization in these cells; succinylated concanavalin A is also inhibitory. The effect of these lectins is abolished by the corresponding sugar haptens. Trypsin and periodate treatment of the cells also inhibits infection, as well as calcium ionophore A23187 and drugs that disrupt microtubules and microfilaments directly, like colchicine, vinblastine and cytochalasin B. These results show that alteration(s) of a surface glycoprotein(s) and/or of the plasma membrane architecture of fibroblastic host cells inhibit infection, suggesting that the surface membrane of these cells does not play a passive role in the process of infection by T. cruzi.
Mol Biochem Parasitol 1981 Apr
PMID:The effect of surface membrane modifications of fibroblastic cells on the entry process of Trypanosoma cruzi trypomastigotes. 701 3

The binding of normal and Plasmodium falciparum-infected squirrel monkey erythrocytes to columns of ligand-coated agarose beads was compared. Concanavalin A, ricin, soybean and peanut agglutinin-coated beads retain erythrocytes containing large developmental stages of the parasite preferentially to ring-containing erythrocytes or to normal erythrocytes. Binding is inhibited by the sugar corresponding to the lectin's specificity. Preferential binding does not occur with wheat germ or Ulex europaeus agglutinin-coated beads. When infected blood is preincubated in immune serum, infected erythrocytes are specifically retained by Protein A-coated beads. These peculiar binding properties reflect modifications of the infected erythrocyte membrane.
Mol Biochem Parasitol 1981 Dec
PMID:Interactions of Plasmodium falciparum infected erythrocytes with ligand-coated agarose beads. 703 41


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