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At least 37 records · Page 2Linked to original sources
PubMed1992

Yeast SNF2/SWI2, SNF5, and SNF6 proteins function coordinately with the gene-specific transcriptional activators GAL4 and Bicoid.

The SNF2 (SWI2), SNF5, and SNF6 genes are required for transcription of many diversely regulated genes in Saccharomyces cerevisiae. Previously, we showed that SNF2, SNF5, and SNF6 function interdependently in transcriptional activation, possibly forming a heteromeric complex. Here, we present evidence that SNF6 has a more direct role in stimulating transcription than SNF2 and SNF5. The global effects of mutations in SNF2, SNF5, and SNF6 suggested that these SNF proteins may function coordinately with many gene-specific activators. We show that LexA-GAL4 and LexA-Bicoid fusion proteins are both dependent on SNF2, SNF5, and SNF6 for activation of target genes containing one or multiple lexA operators. The stringency of the requirement for the SNF proteins varies with the activator, the number of binding sites for the activator, and the target promoter. Thus, these SNF proteins appear to represent a class of intermediary proteins that facilitate transcriptional activation by gene-specific regulatory proteins.

Adenosine Triphosphatases↗
PubMed1977

The chemical properties of out-of-equilibrium states of proteins and the role of these states in protein functioning.

The out-of-equilibrium states of several iron-containing proteins (cytochromes c of different origin, haemoglobin, myoglobin, ferredoxin and other non-haem iron proteins, cytochrome c oxidase, horseradish peroxidase) were recorded after fast changes in the active centre (electron reduction of iron, ligand dissociation). Strained states result in which the active centre has already been changed and undergone vibrational relaxation but the main part of protein globule is in the 'old', now out-of-equilibrium, state. Protein structure and chemical properties in these states differ considerably from those in equilibrium states. As a rule, the rate constants of protein-specific chemical reactions increase in out-of-equilibrium states by 1--3 orders of magnitude in comparison with those in equilibrium states. Spectra and reactivity of these proteins change in the course of slow (up to 10(-1) s) conformational relaxation, continuously approaching the equilibrium values. It seems that this conformational relaxation is essentially the elementary act of many enzymic reactions for which the rate of substrate-product transformation is determined by the rate of this conformational change.

Cytochrome c Group↗
PubMedDate not supplied

Disturbing GTP-binding protein function through microinjection into the visual cell of Limulus.

We have tested the action of three agents microinjected into the ventral nerve photoreceptor of Limulus on the electrical response to dim light. 1. A monoclonal antibody (mAb 4A) against the G alpha subunit of frog transducin reduces the size of the receptor current to 60%, suggesting an interaction with G alpha in the Limulus photoreceptor. 2. Injection of Clostridium botulinum ADP-ribosyltransferase C3 reduces the size to 46%; latency is not affected. The results imply that small GTP-binding proteins play a functional role in photoreception of invertebrates. 3. Injection of GDP-beta-S reduces dose-dependently the size of the receptor current to 15% and prolongs the latency to 200%, presumably by reducing number and rate of G-protein activations.

Animals↗
PubMed1976

Renal function, protein binding and pharmacological response to diazoxide.

1 The effect of rapid (10s) injections of diazoxide was studied in ten hypertensive patients with varying degrees of impairment of renal function. 2 There was a significant correlation between the patient's plasma urea concentration and reduction in mean arterial blood pressure. Diazoxide was also shown to be less highly protein bound in patients with renal failure. 3 It is suggested that the explanation for the increased hypotensive effect of diazoxide observed in patients with reduced renal function is related to higher unbound drug concentrations.

Adult↗
PubMed1992

Bacteriophage and spliceosomal proteins function as position-dependent cis/trans repressors of mRNA translation in vitro.

The translational regulation of ferritin expression currently represents the only well characterized example for eukaryotic translational control by high affinity interactions between a specific cytoplasmic protein, iron regulatory factor [IRF], and an mRNA-binding site, the iron-responsive element [IRE], located in the 5' untranslated region [UTR] of ferritin mRNAs. To elucidate whether IRE/IRF may represent the first physiological example of a more general mechanism for mRNA-specific translational control, high affinity RNA-binding sites for the bacteriophage MS2 coat protein or the spliceosomal protein U1A were introduced into the 5' UTR of capped chloramphenicol acetyltransferase [CAT] transcripts. In the absence of these RNA-binding proteins, CAT mRNA was efficiently translated. Addition of purified MS2 coat protein or U1A caused a specific, dose-dependent repression of CAT biosynthesis in rabbit reticulocyte and wheat germ in vitro translation systems. The translational blockage imposed by the RNA/protein complex was reversible and did not alter the stability of the repressed mRNAs. Translational repression caused by binding of U1A or MS2 proteins to their target mRNAs is shown to be position-dependent in vitro. Thus, mRNA/protein complexes without an a priori role in eukaryotic mRNA translation function as translational effectors with characteristics resembling those of IRE/IRF.

Bacteriophages↗
PubMed2026

Peptide-phosphorodiamidate morpholino oligomer therapy for dysferlinopathy induces pseudoexon skipping and restoration of functional protein.

The dysferlinopathies are a spectrum of autosomal recessive muscle diseases caused by mutations in the dysferlin gene (DYSF). Clinical manifestations vary from asymptomatic hyperCKemia to severe muscle pathology and loss of muscle function. These are designated as limb-girdle muscular dystrophy type 2R (LGMDR2; formerly LGMD2B or Miyoshi myopathy). Among other functions, dysferlin is crucial for plasma membrane repair and maintenance of intracellular calcium homeostasis. In previous studies, we identified 2 independent point mutations deep within introns that cause aberrant DYSF mRNA splicing and the inclusion of pseudoexons within transcripts that diminish protein expression. In this study, we generated and characterized a mouse model for 1 of these mutations (within DYSF intron 44). In these mice, a segment of human DYSF DNA containing the mutant intronic sequence flanked by surrounding human exon sequences replaced the normal homologous mouse DNA. These mice exhibited aberrant Dysf pre-mRNA splicing, pseudoexon inclusion, loss of DYSF protein expression, and muscle pathology similar to that observed in patients. Using this model, we identified antisense oligonucleotides and a peptide-phosphorodiamidate morpholino oligomer that blocks the mouse Dysf pre-mRNA splicing complexes from binding the mutant pre-mRNA, thereby restoring nearly normal muscle pathology and function.

Animals↗
PubMed1992

Rabbit skeletal muscle glycogenin. Molecular cloning and production of fully functional protein in Escherichia coli.

Glycogenin is a self-glucosylating protein involved in the initiation reactions of glycogen synthesis. Initiation occurs in two stages, requiring first the covalent attachment of a glucose residue to Tyr-194 of glycogenin and then elongation to form an oligosaccharide chain. The latter reaction is known to be catalyzed by glycogenin itself. The glycogenin sequence determined from the protein by Campbell and Cohen (Campbell, D. G., and Cohen, P. (1989) Eur. J. Biochem. 185, 119-125) was used to design oligonucleotide probes to screen a rabbit muscle lambda gt11 library. A cDNA was isolated that predicted an amino acid sequence identical to that of Campbell and Cohen, except that Cys residues replaced Ser-88 and Leu-97. Northern analysis indicated a strongly hybridizing message of 1.8 kilobases, present in most tissues including skeletal muscle, but much weaker in kidney and scarcely detectable in liver. A much weaker 3-kilobase message was also detected in muscle. Polymerase chain reaction was used to isolate DNA fragments encoding a portion of glycogenin from rat and cow. The sequence of this segment was > 90% identical at the amino acid level across the three species, indicating that glycogenin is a highly conserved protein. Using the pET-8c vector, the glycogenin protein was expressed in Escherichia coli. Incubation of the recombinant glycogenin with UDP-[14C]glucose and Mn2+ resulted in labeling of the glycogenin protein, indicating that the recombinant glycogenin was enzymatically active and capable of self-glucosylation. Furthermore, after incubation with UDP-glucose, the recombinant glycogenin could serve as a substrate for glycogen synthase, leading to the production of high M(r) polysaccharide. Therefore, production of functional glycogenin did not require the intervention of any other mammalian protein.

Amino Acid Sequence↗
PubMed1992

Functional protein S in women with lupus anticoagulant inhibitor.

Protein C (PC) and protein S (PS) are components of a potent, natural anticoagulant system. A deficiency of one of these two inhibitors is associated with thrombotic events in young people. A significant reduction in functional PS activity has been observed during normal pregnancy, and recurrent fetal loss may occur in women with lupus anticoagulant (LA) inhibitor. We measured functional PS activity and free PS antigen in 16 non pregnant patients with LA inhibitor and in 17 normal women as controls. A significant difference was observed between patients and controls in functional PS activity (65 +/- 23% vs 87 +/- 15%, p = 0.02) but not in free PS antigen (88 +/- 17% vs 93 +/- 17%). Functional PS activity decreased only in six patients (37%). Removal of IgG from plasma reduced the difference in functional PS activity between patients and controls. Immunologic IgG levels did not correlate with anti-phospholipid antibodies (APA) activities, activated partial thromboplastin time/kaolin clotting time (aPTT/KCT) data or functional PS activity.

Abortion, Habitual↗
PubMed2025

An Evolutionary Framework Exploiting Virologs and Their Host Origins to Inform Poxvirus Protein Functions.

Poxviruses represent evolutionary successful infectious agents. As a family, poxviruses can infect a wide variety of species including humans, fish, and insects. While many other viruses are species-specific, an individual poxvirus species is often capable of infecting diverse hosts and cell types. For example, the prototypical poxvirus, vaccinia, is well known to infect numerous human cell types but can also infect cells from divergent hosts like frog neurons. Notably, poxvirus infections result in both detrimental human and animal diseases. The most infamous disease linked to a poxvirus is smallpox caused by variola virus. Poxviruses are large double-stranded DNA viruses, which uniquely replicate in the cytoplasm of cells. The model poxvirus genome encodes ~200 nonoverlapping protein-coding open reading frames (ORFs). Poxvirus gene products impact various biological processes like the production of virus particles, the host range of infectivity, and disease pathogenesis. In addition, poxviruses and their gene products have biomedical application with several species commonly engineered for use as vaccines and oncolytic virotherapy. Nevertheless, we still have an incomplete understanding of the functions associated with many poxvirus genes. In this chapter, we outline evolutionary insights that can complement ongoing studies of poxvirus gene functions and biology, which may serve to elucidate new molecular activities linked to this biomedically relevant class of viruses.

Animals↗