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W Szer

Publications and source records attributed to W Szer.

At least 37 records · Page 2Linked to original sources
PubMed1981

A RNA helix-destabilizing protein is a major component of Artemia salina nuclear ribonucleoproteins.

A major component of 30S heterogeneous nuclear ribonucleoprotein (hnRNP) particles from Artemia salina is HD40, a protein that has been characterized as a RNA helix-destabilizing protein [Marvil, D. K., Nowak, L. & Szer, W. (1980) J. Biol. Chem. 255, 6466-6472; Nowak, L., Marvil, D. K., Thomas, J. O., Boublik, M. & Szer, W. (1980) J. Biol. Chem. 255, 6473-6478]. HD40 binds to and disrupts the secondary structure of nuclear RNA fragments isolated from 30S hnRNP with a stoichiometry of one protein per 10-12 nucleotides. The addition of HD40 in excess of this ratio results in the formation of bead-like HD4-nuclear RNA complexes that are similar in properties and appearance to native 30S hnRNP particles. The heterogeneous nuclear RNA (hnRNA) in the HD40-hnRNA complexes is unstacked and unfolded to about the same extent as the RNA in the native 30S hnRNP particles. HD40 is strikingly similar in molecular weight (40,000) and amino acid composition (no cysteine, high glycine, presence of dimethylarginine, and blocked NH2 terminus) to eukaryotic hnRNP proteins isolated from many cell types. HD40 can be separated into three isoelectric species with basic pIs, which appears to be posttranslational modifications of a single polypeptide chain.

Animals↗
PubMed1980

A single-stranded nucleic acid-binding protein from Artemia salina. I. Purification and characterization.

A protein that binds tightly to single-stranded but not to double-strained nucleic acids has been purified to homogeneity from a high salt wash of ribosomes from cryptobiotic Artemia saline gastrulae. The protein, designated HD40 to indicate a helix-destabilizing protein with a molecular weight of 40,000, is present in the high-salt ribosomal wash at a level of about 2 molecules per 80 S ribosome. The protein is monomeric at salt concentrations from 0.01 to 0.5 M and has an alpha-helix content of approximately 15%. The amino acid composition of HD40 is characterized by a high glycine content (19.5 mol%), the absence of cysteine, and the presence of the unusual amino acid dimethylarginine. The isolated protein binds preferentially to natural RNA over denatured DNA. HD40 inhibits protein synthesis directed by poly(rU) and by Artemia poly(A+) RNA in cell-free systems derived from Artemia and from wheat germ; inhibition is relieved by excess of mRNA. Single-stranded ribo- and deoxyribopolynucleotides are largely protected from degradation by nucleases when complexed with HD40.

Amino Acids↗
PubMed1980

A single-stranded nucleic acid-binding protein from Artemia salina. II. Interaction with nucleic acids.

A helix-destabilizing protein, HD40 (Mr 40,000), isolated from the cytoplasm of Artemia salina (Marvil, D.K., Nowak, L., and Szer, W. (1980) J. Biol. Chem. 255, 6466-6472) stoichiometrically disrupts the secondary structures of synthetic single-stranded and helical polynucleotides (e.g. poly(rA), poly(dA), poly(rC), poly(dC), and poly(rU)) as well as those of natural polynucleotides (e.g. MS2 RNA and phi X174 viral DNA). The conformations of double-stranded DNA and double- or triple-stranded synthetic polynucleotides are not affected by the protein. Formation of duplexes, e.g. poly(rA . rU), is prevented by HD40 at 25 to 50 mM but not at 100 to 140 mM NaCl. The unwinding of the residual secondary structure of RNA and DNA by HD40 is not highly cooperative and has a stoichiometry of one HD40 per 12 to 15 nucleotides. The addition of HD40 in excess of 1 molecule per 12 to 15 nucleotides results in the cooperative formation of distinct bead-like structures along the nucleic acid strand. The beads are about 20 nm in diameter with a center to center distance of about 40 nm. The appearance of the beads is not accompanied by any spectral changes (CD and UV) beyond those obtained at a stoichiometry of one HD40 molecule per 12 to 15 nucleotides.

Animals↗
PubMed1979

Interactions of 4', 6-diamidine-2-phenylindole with synthetic polynucleotides.

4', 6-Diamidine-2-phenylindole forms fluorescent complexes with synthetic DNA duplexes containing AT, AU and IC base pairs; no fluorescent complexes were observed with duplexes containing GC base pairs or with duplexes containing a single AT base pair sandwiched between GC pairs. The binding site size is one molecule of dye per 3 base pairs. The intrinsic binding constants are higher for alternating sequence duplexes than for the corresponding homopolymer pairs. With the exception of the four-stranded helical poly rI which exhibits considerable fluorescence enhancement upon binding of the ligand, none of the single- or multi- stranded polyribonucleotides and ribo-deoxyribonucleotide hybrid structures form fluorescent complexes with the dye. Poly rI is the only RNA which forms a DNA B-like structure (Arnott et al. (1974) Biochem. J. 141, 537). The B conformation of the helix and the absence of guanine appear to be the major determinants of the specificity of the fluorescent binding mode of the dye. Nonfluorescent interactions of the dye with polynucleotides are nonspecific; UV absorption and circular dichroic spectra demonstrate binding to synthetic single- and double-stranded DNA and RNA analogs, including those containing GC base pairs.

Amidines↗
PubMed1979

Nucleic acid binding and unfolding properties of ribosomal protein S1 and the derivatives S1-F1 and m1-S1.

The nucleic acid binding and unwinding properties of wild-type Escherichia coli ribosomal protein S1 have been compared to those of a mutant form and a large trypsin-resistant fragment, both reported recently [J. Mol. Biol. 127, 41-45 (1979) and J. Biol. Chem. 254, 4309-4312 (1979). The mutant (m1-S1) contains 77% and the fragment (S1-F1) 66% of the polypeptide chain length (approximately 600 amino acid residues) of protein S1. The mutant is active in protein synthesis in vitro; the fragment, although retaining one or more of the functional domains of S1, is inactive in protein synthesis. We find that m1-S1 is is almost as effective as S1 in binding to poly(rU), phage MS2 RNA and simian virus 40 (SV40) DNA, and in unfolding poly(rU) and the helical structures present in MS2 RNA and phi X174 viral DNA. S1-F1, however, binds to poly(rU) and denatured SV40 DNA, but not to MS2 RNA. It unfolds neither poly(rU), nor the residual secondary structure of MS2 RNA or phi X174 viral DNA. Thus, there appears to be a correlation between the loss in ability of S1 to unwind RNA and the loss in its ability to function in protein synthesis.

Bacterial Proteins↗
PubMed1977

Nucleic acid helix-unwinding properties of ribosomal protein S1 and the role of S1 in mRNA binding to ribosomes.

The presence of ribosomal protein S1 in 30S ribosomes is indispensable for the formation of 30S initiation complexes with natural mRNA. The 30S subunits lacking S1 retain activity with AUG as mRNA and are also active in poly(rU)-directed binding of Phe-tRNA. Isolated protein S1 stoichiometrically disrupts the secondary structure of helical and stacked single-stranded polynucleotides and converts them into their fully or partially denatured forms. A mono-N-ethylmaleimide derivatives of S1 is nearly devoid of any RNA helix-unwinding properties but is readily incorporated into 30S subunits deficient in S1. The resulting N-ethylmaleimide-S1-containing 30S subunits are completely inactive in the binding of MS2 [3H]RNA and in the formation of an initiation complex with MS2 RNA as mRNA. They retain activity in the binding of the initiator fMet-tRNA in response to the trinucleotide AUG and in the binding of Phe-tRNA in response to poly(U). They also retain the capacity to bind 50S subunits and to form 70S couples. These results suggest that a correlation exists between the RNA helix-unwinding capacity of isolated S1 and the function of S1 in the ribosomal binding of natural mRNA when the protein becomes part of the 30S subunit.

Binding Sites↗
PubMed1976

Inactive form of edeine in the edeine-producing Bacillus brevis Vm 4 cells.

1. Exogenous edeine inhibits the synthesis of DNA and protein, but not that of RNA, in extracts of edeine-producing Bacillus brevis Vm 4 cells. This is analogous to the effect of edeine on extracts obtained from edeine-sensitive cells. 2. Producer cells, in contrast to sensitive ones, are not permeable to exogenous edeine. DNA synthesis in producer cells rendered permeable by toluene treatment becomes sensitive to edeine. 3. No free edeine could be detected in post-log producer cells during maximal synthesis of edeine. Nascent edeine exists in the cell in a biologically inactive form, bound to a fast-sedimenting fraction. Edeine B, identical to the antibiotic present in the medium, is released from this fraction by mild treatment with alkali.

Anti-Bacterial Agents↗
PubMed1975

Ribosomal protein S1 and polypeptide chain initiation in bacteria.

Among several subspecies of 30S subunits of Escherichia coli observed by polyacrylamide-agarose gel electrophoresis, only the slow-moving, protein S1-containing subspecies participates in the formation of the 30S initiation complex with coliphage MS2 RNA as mRNA; the other subspecies retain activity with AUG as mRNA; they are also active in the poly(U)-directed binding of Phe-tRNA. Protein S1 from Caulobacter crescentus substitutes for E. coli S1 despite the fact that C. crescentus ribosomes do not bind MS2 RNA. Under appropriate conditions, the entire population of E. coli 30S subunits can be isolated as the S1-containing subspecies. Protein S1 is lost by salt treatment of ribosomes.

Bacteria↗
PubMed1975

Modification of E. coli ribosomes and coliphage MS2 RNA by bisulfite: effects on ribosomal binding and protein synthesis.

The reaction of E. coli 70s ribosomes with 0.2 M NaH-35 s03 (pH 7.1, 3.5hrs, 37 degree) led to the conversion of 4.5% of the uracil residues of the R, RNA into 5.6-dihydrouracil-6-sulfonate residues. The modified ribosomes exhibited a significant decrease in their ability to bind (14-C)-phenylalanyl-(RNA-phe and to incorporate (14-C)-phenylalanine into protein in the presence of polyuridylic acid. The ability of the modified ribosomes to form an initiation complex as measured by the A-U-G or coliphage MS2 RNA dependent binding of (14-C)-fmet-tRNA-fmet was also impaired, as was their ability to incorporate (14-C) lysine into protein with MS2 RNA as messenger. Treatment os MS RNA with 0.2 M sodium (35-S) bisulfite, pH 7.0 at 25 degrees C resulted in the substitution of 2.7% and 6.2% of the uracil residues by bisulfite after 1 and 3.5 hrs of reaction, respectively. Impairment of function of the MS2 RNA in both initiation complex formation and transplantation assays was observed. These reactions of uracil residues of mRNA and rRNA may be a cause of biological damage inflicted by sodium bisulfite and sulfur dioxide.

Bacterial Proteins↗
PubMed1974

Replacement of ribosomal protein S1 by interference factor ialpha in ribosomal binding of phage Ms2 RNA.

The MS2 RNA binding capacity of 30S ribosomal subunits, which is lost when protein S1 is removed, can be restored following incubation with interference factor ialpha and repelleting. Polyacrylamide-agarose gel electrophoresis shows that, under these conditions, a faster moving, non-RNA binding 30S species, which contains no S1, is converted to a slower moving RNA-binding one, having the same mobility as the 30S species that contains protein S1. Factor ialpha binds to single-stranded RNAs in a pattern that closely resembles the RNA binding pattern of initiation factor IF-3.

Bacterial Proteins↗
PubMed1974

Interaction of Escherichia coli 30S ribosomal subunits with MS2 phage RNA in the absence of initiation factors.

MS2 RNA binds at 0 degrees to 30S subunits from E. coli and, to a smaller extent, to those of a Pseudomonas species, as judged by filtration on nitrocellulose membranes; this mRNA does not bind to 30S subunits from Bacillus brevis or Caulobacter crescentus. Binding does not depend on the presence of initiation factors; it is sensitive to aurintricarboxylic acid but insensitive to edeine and is competitive with such synthetic polynucleotides as poly(U) and poly(AUG). Complex formation can also be detected by electrophoresis on polyacrylamide-agarose gels. By this procedure, E. coli 30S subunits are separated into two major components. Only the more slowly moving component, which contains the ribosomal protein S1, interacts with the RNA.

Anti-Bacterial Agents↗