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At least 991 records · Page 55Linked to original sources
PubMed1988

Polyspecificity of human monoclonal antibodies reactive with Mycobacterium leprae, mitochondria, ssDNA, cytoskeletal proteins, and the acetylcholine receptor.

The origin of autoantibodies against ubiquitous autoantigens (e.g., single-stranded (SS) DNA, cytoskeletal proteins, mitochondria) is obscure. Patients with lepromatous leprosy have many such autoantibodies in their serum. In order to study the polyspecificities of human autoantibodies expressed during infection with Mycobacterium leprae we prepared human monoclonal antibodies derived from the fusion of peripheral blood lymphocytes of a patient with lepromatous leprosy to the human lymphoblastoid line GM 4672. Hybridomas were tested for binding to a DNAse-treated sonicate of M. leprae and a panel of autoantigens. Of the primary (uncloned) cultures, 14% bound ssDNA, 35% bound M. leprae, 11% bound both M. leprae and ssDNA, and 16% bound to mitochondria. Several also bound to the acetylcholine receptor of Torpedo marmorata. Monoclonal antibodies derived from separate primary cultures revealed similar cross-reactions between several autoantigens and M. leprae. In addition, one antibody was identified which bound to mitochondria and the acetylcholine receptor, and which was recognized by an anti-idiotypic antibody which bears the "internal image" of the acetylcholine receptor. These results suggest that antigenic mimicry may play a role in eliciting autoantibody expression from the immune repertoire.

Animals↗
PubMed1993

Folding in vivo of bacterial cytoplasmic proteins: role of GroEL.

A general role for chaperonin ring structures in mediating folding of newly translated proteins has been suggested. Here we have directly examined the role of the E. coli chaperonin GroEL in the bacterial cytoplasm by production of temperature-sensitive lethal mutations in this essential gene. After shift to nonpermissive temperature, the rate of general translation in the mutant cells was reduced, but, more specifically, a defined group of cytoplasmic proteins--including citrate synthase, ketoglutarate dehydrogenase, and polynucleotide phosphorylase--were translated but failed to reach native form. Similarly, a monomeric test protein, maltose-binding protein, devoid of its signal domain, was translated but failed to fold to its native conformation. We conclude that GroEL indeed is a machine at the distal end of the pathway of transfer of genetic information, assisting a large and specific set of newly translated cytoplasmic proteins to reach their native tertiary structures.

ATP-Binding Cassette Transporters↗
PubMed1994

Copurification of E. coli RNAase E and PNPase: evidence for a specific association between two enzymes important in RNA processing and degradation.

Ribonuclease E (RNAase E) was isolated in a complex that also contained polynucleotide phosphorylase (PNPase). Besides copurification, evidence for an association of these enzymes comes from sedimentation and immunoprecipitation experiments. Highly purified RNAase E correctly processed E. coli 5S ribosomal RNA, bacteriophage T4 gene 32 mRNA and E. coli ompA mRNA at sites known to depend on the rne gene for cleavage in vivo. The difference between previous smaller estimates of the size of RNAase E and that reported here apparently is due to the sensitivity of the enzyme to proteolysis during purification. The discovery of a specific association between RNAase E and PNPase raises the intriguing possibility that these enzymes act cooperatively in the processing and degradation of RNA.

Endoribonucleases↗
PubMed1984

Binding of divalent copper and calcium ions to poly I.

The effect of Cu2+ ions on the ultraviolet differential ( UVD ) spectra of single-stranded poly I was studied and the coordination (delta epsilon b) and conformation (delta epsilon c) components of the spectra calculated. The comparison of delta epsilon b and the UVD spectrum of protonated IMP leads to the conclusion that N(7) of inosine-5'-monophosphate (IMP) is a coordinating site for Ca2+ and Cu2+ ions on the polymer bases. The binding of Ca2+ and Cu2+ ions causes differently directed displacements of the four absorption bands of poly I, which are observed in the wavenumber range (50-34) X 10(3) cm-1. The calculation of concentration dependencies for the association constants (K") of Ca2+ and Cu2+ ions binding to poly I bases shows that the binding is cooperative. The K" values for the poly I + Ca2+ complex are two orders of magnitude lower than those for the poly I + Cu2+ complex. At low ion concentrations, binding to the poly I phosphates predominates and increases the degree of the polynucleotide helicity. At higher concentrations the spectra are mainly affected by the ion binding to bases, which results in melting of the helical parts of poly I. At Ca2+ concentrations exceeding 10(-3) M light-scattering aggregates are formed. The degree of monomer order in them is close to that observed in multistranded helices of poly I.

Calcium↗
PubMed1985

Studies of bivalent copper ion binding to poly C.

Ultraviolet differential spectra of single-stranded poly C, taken in the presence of Cu2+ ions, are studied at various ionic strengths and temperatures. Coordinational and conformational components of these spectra are obtained. The Cu2+ ion coordination site on the polynucleotide bases is found to be N(3) and possibly O(2). The direction of the poly C absorption band shift due to ion binding and conformational transitions is established. At low ionic strengths of the solution Cu2+ ions cause the helical parts of poly C to melt. At high ones the formation of double-stranded parts was observed in addition to the above effect. The calculated concentration dependences of ion-poly C bases association constants show that binding is cooperative at any ionic strength.

Copper↗
PubMed1988

Practical aspects of 2D NMR for assigning the non-exchangeable protons in DNA-RNA fragments.

Using the branched trimer A2'-5'A3'-5'A as an example, different 2D NMR experiments such as homonuclear correlations via single-quantum coherence, double-quantum filtration via double-quantum coherence, isotropic mixing, relayed connectivities, cross relaxation and 31P/1H correlations are presented together with the corresponding spectra. The discussion pointed out the advantages and the difficulties of 14 pulse sequences, used for assigning non-exchangeable protons in DNA or RNA fragments. The emphasis has been put on the methodological aspects of 2D NMR as a simple technique, allowing an easier assimilation of the new coming 2D NMR pulse sequences.

Adenine Nucleotides↗
PubMed1981

Antiviral effects of single-stranded polynucleotide inhibitors of the influenza virion-associated transcriptase against influenza virus infection of hamsters and ferrets.

Administration of a single-stranded polynucleotide copolymer containing 9% cytidine residues and 91% 4-thiouridine residues [poly(C,S4U10)], a known potent inhibitor of the virion transcriptase of influenza viruses, suppressed the amount of virus recoverable from the nasal washes of influenza virus-infected hamsters and ferrets. The incidence of sneezing and nasal discharge in infected ferrets was also reduced. In hamsters, poly(C,S4U10) was more effective than amantadine-HCl or Virazole. Polyinosinic acid in combination with poly-5-hydroxy cytidylic acid also had anti-influenza effects. Poly(C,S4U10) annealed to polyadenylic acid was not effective, nor was the double-stranded polymer (polyinosinic acid) . (polycytidylic acid) even when complexed with carboxymethylcellulose and polylysine. No toxic effects of poly(C,S4U10) were apparent in the treated hamsters and ferrets, and high doses (greater than or equal to 2.86 g/kg) administered intraperitoneally to mice produced no adverse effects.

Animals↗
PubMed1984

Preparation and biological properties of a highly active poly(G) X poly(C) inducer of interferon.

Experimental conditions necessary for the full expression of interferon-inducing activity by a complex of polyguanylic acid and polycytidylic acid included: (i) a sufficiently high molecular size of each homopolymer; (ii) annealing conditions which insured complete denaturation of polyguanylic acid self-structure; and (iii) the specific biological assay employed to assay interferon-inducing potency. The complex of polyguanylic acid and polycytidylic acid possessed several properties that suggested it may be an atypical polynucleotide interferon inducer. For instance, it was inactive in primary rabbit kidney cell cultures, usually exquisitely sensitive to polynucleotide interferon inducers, unless it was incubated on the cell cultures for prolonged times or in the presence of DEAE-dextran. Polyguanylic acid X polycytidylic acid could induce interferon in rabbits and mice but gave a more protracted response than did poly(I) X poly(C). Finally, poly(G) X poly(C) was, without any modification, resistant to degradation by serum nucleases.

Animals↗
PubMedDate not supplied

Mismatched dsRNA (ampligen) induces protection against genomic variants of the human immunodeficiency virus type 1 (HIV-1) in a multiplicity of target cells.

Mismatched double-stranded RNA of the form r(I)n.r(C12-U)n (Ampligen) has been shown to be active against human immunodeficiency virus type 1 (HIV-1) using CEM and C3 cells as targets for infection by the highly similar HIV-1 isolates HTLV-IIIB and LAV (Montefiori, D.C. and Mitchell, W.M., 1987, Proc. Natl. Acad. Sci. U.S.A., 84, 2985-2989). The scope of Ampligen's anti-HIV-1 activity was examined in this study using the genetically divergent HIV-1 isolate HTLV-IIIRF, two additional target T-cell lines, H9 and MT-2, and a monocyte/macrophage cell line, U937. As judged by indirect immunofluorescence, reverse transcriptase activity and vital dye uptake, Ampligen was active against HTLV-IIIRF in H9, MT-2, C3 and U937 cells in addition to being active against HTLV-IIIB in U937 cells. A minimum of 1 h preincubation of cells (MT-2) with Ampligen was required for maximum activity. These results suggest that Ampligen's potential clinical efficacy may not be limited by either the highly variable nature or host cell range of HIV-1.

Antiviral Agents↗
PubMed1981

Ribonuclease of Entamoeba invadens.

Two bands of RNAase activity were observed on gel electrophoresis of fractions obtained during partial purification of the RNAase of Entamoeba invadens. The faster migrating band which was responsible for most of the RNAase activity was isolated by gel electrophoresis. A pI of 5.5 was determined for this RNAase activity and estimates of its molecular weight and sedimentation coefficient gave values of about 25 000 and approximately 2.8 S. It exhibited maximum activity around pH 6, and digestion of RNA showed a pattern expected of an endoribonuclease.

Animals↗