Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this paper we examine the binding of Escherichia coli transcription termination factor rho to single-stranded RNA. Random polyribonucleotide copolymers containing low ratios of the fluorescent base 1,N6-ethenoadenosine have been synthesized using polynucleotide phosphorylase. Binding of rho to these polynucleotides elicits a significant increase in fluorescence, thus allowing either the direct monitoring of the titration of these polynucleotides with rho or measurement of the competitive displacement of the protein from these probes with other nucleic acids, even in the presence of biologically significant concentrations of ATP. By these techniques, it is shown that the binding site size (n) of rho protein to polynucleotides is 13(+/- 1) nucleotide residues per rho monomer (or 78(+/- 6) nucleotide residues per rho hexamer). Binding constants (K) and co-operativity parameters (omega) for the binding of rho to these polynucleotides have been measured as a function of nucleotide composition and of salt concentration. The results show that the affinity of rho for cytosine residues is quite strong and salt concentration independent, whilst binding to uridine residues is somewhat weaker and very salt concentration dependent. Poly(rC) and poly(dC) bind to rho competitively and with equal affinity and site size, although poly(rC) is the strongest cofactor for activating rho-dependent ATPase and poly(dC) has no ATPase cofactor activity at all. It is also shown that ATP (or ADP or ATP-gamma-S) binding does not change the binding site size of rho on RNA nor decrease its affinity for RNA binding. Circular dichroism measurements of rho binding to phage R17 RNA suggest that the affinity (K omega) of rho for RNA may be increased by ATP. The possible significance of these results for models of rho-dependent transcription termination is discussed in the companion paper.
J Mol Biol 1988 Feb 20
PMID:Interactions of Escherichia coli transcription termination factor rho with RNA. I. Binding stoichiometries and free energies. 245 Oct 28

The mitochondrial respiratory system is absent in slender bloodstream forms of Trypanosoma brucei, incomplete in stumpy bloodstream forms, and complete in procyclic (insect) forms. The steady-state abundance of transcripts of some mitochondrially encoded components of the respiratory system correlates with its differential expression in different life cycle stages. Recently, it was reported that uridines which are not encoded in the genome are added to cytochrome b and cytochrome oxidase II transcripts. We now report that the (U)+ transcripts of both genes are found in procyclic forms and to some degree in stumpy forms but are absent in slender forms. The uridine additions to cytochrome oxidase II correct a frameshift in the gene and presumably allow production of a full-length protein, whereas those added to cytochrome b create an in-frame AUG which extends the N terminus of the predicted protein by 20 amino acids. The stage specificity of uridine additions to these transcripts thus reflects the life cycle stage during which the protein products would be used. Transcripts of MURF2, a gene of unknown function, have additional uridines in both slender and procyclic forms which create two in-frame AUGs. MURF2 transcripts additionally differ from the DNA sequence in ways which cannot be explained by uridine addition alone, implying that other processes alter these transcripts.
Mol Cell Biol 1988 Mar
PMID:Developmental aspects of uridine addition within mitochondrial transcripts of Trypanosoma brucei. 245 74

The possible mediatory role of cAMP in the induction of oocyte maturation by luteinizing hormone (LH) is not yet clear since evidence for both inhibitory and stimulatory actions of the nucleotide on the oocyte has been provided. To elucidate the role of cAMP in regulation of oocyte meiosis we tried in the present study to dissociate between the inhibitory and stimulatory action of this nucleotide on oocyte maturation. To induce maturation, oocytes enclosed by their follicles were transiently exposed to either dibutyryl cAMP (dbcAMP) or to the phosphodiesterase inhibitor methylisobutylxanthine (MIX). Inhibition of maturation was obtained by the addition of the above agents to either follicle-enclosed oocytes incubated in the presence of LH or isolated cumulus-free oocytes that mature spontaneously in vitro. We found that inhibition of oocyte maturation is obtained by a relatively low dose of either dbcAMP or MIX while higher concentrations of these agents are required to induce oocyte maturation. Coupling of the oocyte to the cumulus cells, as expressed by the fraction of labeled uridine transferred from the cumulus cells to the oocyte following exposure of the follicle-enclosed cumulus-oocyte complex to MIX, was also determined. We found that uncoupling of the oocyte from the cumulus cells corresponded with the induction, but not inhibition of oocyte maturation, both by its concentration dependence and time-course. We suggest that cAMP has a dual role in regulation of oocyte maturation. Lower levels of the nucleotide act to maintain meiotic arrest, while elevated levels of cAMP mediate LH action to induce meiosis resumption.
Mol Cell Endocrinol 1988 Mar
PMID:Dissociation between the inhibitory and the stimulatory action of cAMP on maturation of rat oocytes. 245 85

A rapid sampling technique was used to follow nucleoside uptake by Trichomonas vaginalis. The results indicated that nucleoside uptake is biphasic with time. Adenosine, guanosine, and uridine uptake is carrier mediated, transported substrate is rapidly metabolised to nucleotides. Two separate carriers appear to exist, one which transports all nucleosides and a second which transports adenosine, guanosine and uridine. Both carriers have more than one binding site for nucleosides. The first carrier has sites for adenosine and pyrimidine nucleosides, and a separate site for purine nucleosides. The second carrier has a site for adenosine and uridine and a separate site for guanosine. Adenosine uptake could not be completely inhibited by nitrobenzylthionucleosides. The rate of nucleoside uptake by T. vaginalis is sufficient to sustain growth.
Mol Biochem Parasitol 1988 Jun
PMID:Nucleoside uptake by Trichomonas vaginalis. 245 3

The trmD operon is a four-cistron operon in which the first and fourth genes encode ribosomal proteins S16 (rpsP) and L19 (rplS), respectively. The second gene encodes a 21,000 Mr polypeptide of unknown function and the third gene (trmD) encodes the enzyme tRNA(m1G37)methyltransferase, which catalyzes the formation of 1-methylguanosine (m1G) next to the 3' end of the anticodon (position 37) of some tRNAs in Escherichia coli. Here we show under all regulatory conditions studied, transcription initiates at one unique site, and the entire operon is transcribed into one polycistronic mRNA. Between the promoter and the first gene, rpsP, an attenuator-like structure is found (delta G = -18 kcal; 1 cal = 4.184 J), followed by four uridine residues. This structure is functional in vitro, and terminates more than two-thirds of the transcripts. The different parts of the trmD operon mRNA decay at a uniform rate. The stability of the trmD mRNA is not reduced with decreasing growth rate, which is in contrast to what has been found for other ribosomal protein mRNAs. Furthermore, earlier experiments have shown the existence of differential expression as well as non-co-ordinate regulation within the operon. Our results are consistent with the regulation of the trmD operon being due to some mechanism(s) operating at the post-transcriptional level, and do not involve differential degradation of different mRNA segments, internal promoters or internal terminators.
J Mol Biol 1989 Aug 20
PMID:Differentially expressed trmD ribosomal protein operon of Escherichia coli is transcribed as a single polycistronic mRNA species. 247 11

The nucleotide sequences of the complete set of tRNA species in Mycoplasma capricolum, a derivative of Gram-positive eubacteria, have been determined. This bacterium represents the first genetic system in which the sequences of all the tRNA species have been determined at the RNA level. There are 29 tRNA species: three for Leu, two each for Arg, Ile, Lys, Met, Ser, Thr and Trp, and one each for the other 12 amino acids as judged from aminoacylation and the anticodon nucleotide sequences. The number of tRNA species is the smallest among all known genetic systems except for mitochondria. The tRNA anticodon sequences have revealed several features characteristic of M. capricolum. (1) There is only one tRNA species each for Ala, Gly, Leu, Pro, Ser and Val family boxes (4-codon boxes), and these tRNAs all have an unmodified U residue at the first position of the anticodon. (2) There are two tRNAThr species having anticodons UGU and AGU; the first positions of these anticodons are unmodified. (3) There is only one tRNA with anticodon ICG in the Arg family box (CGN); this tRNA can translate codons CGU, CGC and CGA. No tRNA capable of translating codon CGG has been detected, suggesting that CGG is an unassigned codon in this bacterium. (4) A tRNATrp with anticodon UCA is present, and reads codon UGA as Trp. On the basis of these and other observations, novel codon recognition patterns in M. capricolum are proposed. A comparatively small total, 13, of modified nucleosides is contained in all M. capricolum tRNAs. The 5' end nucleoside of the T psi C-loop (position 54) of all tRNAs is uridine, not modified to ribothymidine. The anticodon composition, and hence codon recognition patterns, of M. capricolum tRNAs resemble those of mitochondrial tRNAs.
J Mol Biol 1989 Sep 05
PMID:Codon recognition patterns as deduced from sequences of the complete set of transfer RNA species in Mycoplasma capricolum. Resemblance to mitochondria. 247 13

A DNA fragment encoding kanamycin resistance was inserted in vitro into a plasmid-borne prs gene encoding phosphoribosylpyrophosphate synthetase of Escherichia coli. The resulting plasmids were subsequently transferred to the chromosome by homologous recombination and the haploid strains prs-3::KanR and prs-4::KanR were obtained. These strains were fully viable, but required guanosine, uridine, histidine, tryptophan and nicotinamide mononucleotide. There was no phosphoribosylpyrophosphate synthetase activity or phosphoribosylpyrophosphate pool in the mutant strains. These results show that phosphoribosylpyrophosphate synthetase is dispensable for E. coli.
Mol Microbiol 1989 Nov
PMID:Phosphoribosylpyrophosphate (PRPP)-less mutants of Escherichia coli. 248 7

In vitro rat germ cell RNA synthesis is influenced by growth factors. Basic fibroblast growth factor (0.1 to 100 ng/ml) increases [3H]uridine incorporation in round spermatids (RS) but not in pachytene spermatocytes (PS); this effect is potentiated by insulin (10 micrograms/ml) and blocked in the presence of Sertoli cell-secreted proteins (SCSP). Somatomedin C (0.1 to 100 ng/ml) exhibits a similar effect when used alone without an influence by SCSP. Transforming growth factor beta (0.1 to 10 ng/ml) acts on both cell types, but SCSP amplify this effect only in PS. These data suggest that growth factors synthesized in situ may play a role in the germ cell development and that their effects are modulated by SCSP.
Mol Reprod Dev 1989
PMID:In vitro effects of growth factors on rat germ cell RNA synthesis and their modulation by Sertoli cell-secreted proteins. 248 13

The ectoplacental cone (EPC) of the Day 7.5 mouse embryo consists of a core of adhesive, proliferating trophoblast cells which transform to invasive trophoblast giant cells during implantation. Adhesive trophoblast cell types express monoclonally defined lactosaminoglycans (LAGs) at the cell surface; transformation to giant cells results in a loss of LAG cell surface expression (H. J. Hathaway and B. S. Babiarz, 1988, Cell Differ. 24, 55-66). LAGs can serve as substrates for cell surface galactosyltransferase (GalTase), providing an adhesive mechanism between a number of different cell types (B. D. Shur, 1984, Mol. Cell. Biochem. 61, 143-158). It was hypothesized that the LAGs in the EPC represented a substrate for a similar GalTase-mediated cell:cell adhesion system. Cell surface GalTase activity was demonstrated on EPC trophoblast on Day 7.5 of development by the incorporation of galactose from exogenous radiolabeled substrate. In 24- to 48-hr EPC trophoblast cultures the enzyme was localized by immunofluorescence to areas of cell:cell contact. Monolayers of differentiated trophoblast giant cells lacked this labeling pattern. The cell surface glycopeptide substrate for GalTase eluted as a single peak with an apparent molecular mass of 15,000 Da. A portion of this material was sensitive to endo-beta-galactosidase digestion, indicating that it contained a LAG structure. Perturbation of the enzyme:substrate complex in 24- to 48-hr EPC outgrowths, with alpha-lactalbumin, uridine 5'-diphosphogalactose, or anti-GalTase antibody, resulted in the disruption of cell:cell contacts. Differentiation to trophoblast giant cells resulted in a loss of sensitivity to surface GalTase perturbation. The results suggest that adhesive EPC trophoblast cells possess a GalTase-mediated cell:cell adhesion system which is downregulated upon differentiation to invasive trophoblast giant cells.
 ...
PMID:Analysis of cell surface galactosyltransferase activity during mouse trophectodermal differentiation. 250 Nov 26

The rodC1 mutation of Bacillus subtilis is a temperature-sensitive marker which affects the levels of teichoic acid synthesis and the cellular morphology. We have determined the nucleotide sequence of the bicistronic operon which contains the rodC gene and the nucleotide sequence of the rodC1 mutant allele. The temperature-sensitive phenotype of the rodC mutant is the result of a single base-pair change. A cytosine to thymine transition in the non-coding strand results in the replacement of a serine residue in the wild-type protein with a phenylalanine residue in the mutant protein. The other gene in the operon, the rodD gene, appears to be equivalent to the gtaA gene which encodes uridine diphosphate-glucose poly-(glycerol phosphate) alpha-glucosyl transferase, an enzyme involved in techoic acid synthesis. This is the first nucleotide sequence analysis of both the wild-type and mutant alleles of a morphogene in B. subtilis.
Mol Microbiol 1989 Sep
PMID:The nucleotide sequence of the rodC operon of Bacillus subtilis. 250 71


<< Previous 1 2 3 4 5 6 7 8 9 10