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Results for “oligomerization”

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At least 19 recordsLinked to original sources
PubMed1979

Different specific activities of the monomeric and oligomeric forms of plasmid DNA in transformation of B. subtilis and E. coli.

(1) The low residual transforming activity in preparations of monomeric, supercoiled, circular (CCC) forms of the plasmids pC194 and pHV14 could be attributed to the presence in such isolates of a small number of contaminating multimeric molecules. (2) E. coli derived preparations of pHV14, as in vitro recombinant plasmid capable of replication in both E. coli and B. subtilis, contain oligomeric forms of plasmid DNA in addition to the prevalent monomeric CCC form. The specific transforming activity of pHV14 DNA for E. coli is independent of the degree of oligomerization, whereas in transformation of B. subtilis the specific activity of the purified monomeric CCC molecules is at least four orders of magnitude less than that of the unfractionated preparation. (3) Oligomerization of linearized pHV14 DNA by T4 ligase results in a substantial increase of specific transforming activity when assayed with B. subtilis and causes a decrease when used to transform E. coli.

Bacillus subtilis↗
PubMed2025

Oligomerization and positive feedback on membrane recruitment encode dynamically stable PAR-3 asymmetries in the C. elegans zygote.

Studies of PAR polarity have emphasized a paradigm in which mutually antagonistic PAR proteins form complementary polar domains in response to transient cues. A growing body of work suggests that the oligomeric scaffold PAR-3 can form unipolar asymmetries without mutual antagonism, but how it does so is largely unknown. Here we combine single molecule analysis and modeling to show how the interplay of two positive feedback loops promotes dynamically stable unipolar PAR-3 asymmetries in early C. elegans embryos. First, the intrinsic dynamics of PAR-3 membrane binding and oligomerization encode negative feedback on PAR-3 dissociation. Second, membrane-bound PAR-3 promotes its own recruitment through a mechanism that requires the anterior polarity proteins PAR-6 and PKC-3. Using a kinetic model tightly constrained by our experimental measurements, we show that these two feedback loops are individually required and jointly sufficient to encode dynamically stable and locally inducible unipolar PAR-3 asymmetries in the absence of posterior inhibition. Given the central role of PAR-3, and the conservation of PAR-3 membrane-binding, oligomerization, and core interactions with PAR-6/PKC-3, these results have widespread implications for PAR-mediated polarity in metazoa.

Journal Article↗
PubMed1977

Electron microscopy of an oligomeric protein stabilized by polyfunctional cross-linking.

Oligomeric proteins can be intramolecularly cross-linked with polylysine in a reaction in which a water soluble carbodiimide mediates an amide linkage between the protein carboxyl groups and the epsilon-amino groups of polylysine. Studies carried out with a cytochrome p-450 indicate that a small number of molecules in a population which has been cross-linked in this way retain important features of their tertiary and quaternary structure when negatively stained and examined in the electron microscope. Use of the method in determining the subunit geometry of oligomeric proteins is discussed.

Catalase↗
PubMed2026

Activation of pro-survival autophagy by a small molecule promoting p62 oligomerization.

Autophagy is a critical mechanism of cellular quality control, orchestrated by selective autophagy receptor (SAR) proteins. Pharmacologically enhancing the cargo-targeting capacity of SARs presents an attractive but underexplored strategy for the precise therapeutic activation of autophagy. Here, we characterize SQ-1, a small-molecule activator of autophagy that engages the prototypical SAR protein p62/sequestosome-1 (SQSTM1). We show that SQ-1 sensitizes p62 to oxidation and promotes its disulfide-mediated oligomerization in response to mitochondrial reactive oxygen species (ROS). This ROS-dependent activation of p62-mediated selective autophagy enhances the clearance of ROS-generating mitochondria and restores cell viability in models of Niemann-Pick type C1 disease, which is marked by impaired autophagic flux. In summary, the unique mode of action of SQ-1 enables self-regulated autophagy activation, offering a potential therapeutic strategy for lysosomal storage disorders and a broader spectrum of age-related diseases characterized by defective autophagy.

Niemann-Pick type C1 disease↗
PubMed1979

The effect of clays on the oligomerization of HCN.

The reaction of 0.1 M HCN and dilute solutions of diaminomaleonitrile (DAMN) at pH 8--9 and 25 degrees C in the presence of suspensions of montmorillonite (bentonite) clays were investigated. Montmorillonite clays inhibit the oligomerization of aqueous solutions of HCN. Yields of colored oligomers, ura, and DAMN, are all diminished by clays, but the rate of loss of cyanide is not significantly decreased. The inhibition of oligomer formation is due to the clay-catalyzed decomposition of DAMN. The absence of strong binding of DAMN to clays was suggested by our failure to detect DAMN when a clay that had been incubated with DAMN was washed with spermidine (6 x 10(-3) g/liter). It was established that DAMN does not simply bind to the clays by the observation that the bulk of the radioactivity was recovered from the supernatant in the reaction of 14C-DAMN with montmorillonite. The clay-catalyzed decomposition of DAMN was observed when montmorillonite from two different sources was used and with a variety of homoinic montmorillonites and bentonites. A modification of the established procedure for using the cyanide electrode for cyanide analyses was used to follow the release of HCN from DAMN. This new method can be used in both the acidic and basic pH range and it does not result in the destruction of DAMN by the reagents used for the analysis. Quantitative analyses of the reaction solution from the clay-catalyzed decomposition of DAMN revealed the formation of 1--2 equivalents of HCN per mole of DAMN. The possible significance of these clay-catalyzed reactions in chemical evolution is discussed.

Bentonite↗
PubMed2026

Small GTPase RAN-driven PNET2 oligomerization and phase separation at the nuclear lamina promote nuclear envelope integrity in plants.

The nuclear envelope is a fundamental organizer of eukaryotic cells, yet how plants regulate its architecture and integrity remains poorly understood. In this study, we identified the plant inner nuclear membrane protein PLANT NUCLEAR ENVELOPE TRANSMEMBRANE 2 (PNET2) as a scaffold that maintains nuclear envelope integrity and genome stability. Loss of PNET2 function compromises nuclear membrane structure and sensitizes cells to DNA damage, whereas overexpression drives aberrant nuclear membrane expansion. Biochemically, PNET2 cooperates with the nuclear lamin protein KAKU4 and CROWDED NUCLEI 1 within the nuclear lamina to promote nuclear membrane remodeling, a process driven by biomolecular condensate formation via their intrinsically disordered regions. We further uncovered a direct interaction between PNET2 and the small GTPase RAN. Structural modeling and biochemical analyses revealed that its active GTP-bound form stimulates PNET2 oligomerization, potentially promoting its phase separation to drive membrane expansion. Genetic analyses showed that PNET2 and RAN function in a shared pathway essential for nuclear membrane integrity. Together, our findings define a regulatory module that orchestrates GTPase signaling to sustain nuclear membrane homeostasis in plants, positioning PNET2 as a nexus linking membrane dynamics, nuclear lamina organization, and genome protection.

PNET2↗
PubMed1979

Simian virus 40 recombinants are produced at high frequency during infection with genetically mixed oligomeric DNA.

Classical approaches to analysis of mitotic recombination by use of simian virus 40 (SV40) are limited in usefulness because of low frequencies of recombination. To bypass the apparent rate-limiting step in normal SV40 recombination, oligomeric SV40 was constructed in vitro by ligation of mixtures of pairs of linear DNAs carrying genetically distinct temperature-sensitive mutations. Cultured monkey cells infected with the unfractionated ligation products yielded frequencies of nonparental recombinant progeny that were increased up to 500-fold relative to cells infected with a mixture of the untreated circular molecules. Pairwise crosses were performed with tsB4, tsB8, and tsBC11 DNAs, using unfractionated oligomers constructed from linear molecules cleaved by EcoRI or BamHI. In each cross the fraction of progeny with nonparental genotypes was roughly proportional to the physical distances between the mutant sites. These results suggest a random, rather than site-specific, conversion of oligomers to monomers. Somewhat surprisingly, nonligated mixtures of linear tsB4 and tsB8 DNAs, created by EcoRI digestion, produced a 40-t to 100-fold increase in the frequency of nonparental progeny. These results indicate that intermolecular associations must occur with fairly high efficiency between these linear molecules.

Cell Line↗
PubMed1979

Rotational motion and evidence for oligomeric structures of sarcoplasmic reticulum Ca2+-activated ATPase.

The rotational motion of the sarcoplasmic reticulum Ca2+-activated ATPase (ATP phosphohydrolase, EC 3.6.1.3) has been investigated by measuring the decay of laser flash-induced dichroism with the covalently attached triplet probe eosin isothiocyanate. The Arrhenius plot for rotational mobility indicates two discontinuities at approximately 15 degrees C and approximately 35 degrees C. The experimental data are rationalized in terms of a sudden conformeric change in the ATPase at 15 degrees C and a temperature-dependent equilibrium existing between the conformationally altered ATPase and oligomeric forms of it in the temperature range 15-35 degrees C. The enzymatic activity, as indicated by a discontinuity in the Arrhenius plot for the rate of ATP hydrolysis, appears to be sensitive only to the change at 15 degrees C. There is a strong correlation between the activation energy below 15 degrees C for rotational motion (33.6 +/- 2.2 kcal/mol) and enzymatic activity (34 +/- 4 kcal/mol).

Animals↗
PubMed2025

The small bacterial membrane protein YohP induces nucleoid condensation in E. coli and inhibits oligomerization of antimicrobial peptides.

Prokaryotic organisms execute multiple stress response mechanisms in order to cope with rapidly changing environments. Some mechanisms respond to specific cues, such as the OxyR-dependent response to hydrogen peroxide or the SOS-response that is induced upon DNA-damage. These specific responses complement general mechanisms that respond to multiple and diverse stressors. One example is nucleoid condensation, which is a rapid and effective mechanism for genome protection and observed in response to various stresses, including entry into stationary phase. Recently, the upregulation of small membrane proteins (SMPs) in response to stress was observed, but details on how this emerging class of proteins modulate the stress response is largely unknown. Here, we demonstrate that the production of two SMPs, YohP and YncL, cause nucleoid condensation in Escherichia coli. Nucleoid condensation is the result of YohP-/YncL-induced sublethal membrane depolarization, which induces the phage-shock response and leads to a reduction of global protein synthesis. YohP production also prevents the oligomerization of the antimicrobial peptide magainin-2 in the E. coli membrane and reduces the metabolic activity of E. coli cells. Thus, the synthesis of YohP and likely of other SMPs potentially protects bacterial cells against some unfavorable conditions by shifting them into a metabolically silent state.

YncL↗
PubMed1977

Two Escherichia coli fructose-6-phosphate kinases. Preparative purification, oligomeric structure and immunological studies.

Two isoenzymes of fructose-6-phosphate kinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) are present in Escherichia coli K12. One isoenzyme is allosterically inhibited by phosphoenolpyruvate and activated by nucleoside diphosphates, and is a tetramer composed of four subunits of molecular weight 35 000. A simple method for the purification of this enzyme is reported. Equilibrium dialysis indicates that there are four ATP sites and four GDP sites per tetramer. The second isoenzyme is present in low quantity in wild type bacteria. This enzyme is devoid of allosteric properties. A complete method of purification is described. Determination of its molecular weight under native and denaturing conditions indicates that this protein is a dimer composed of two subunits of molecular weight 36 000. Antisera have been produced against both isoenzymes. The antiserum against one isoenzyme does not cross-react with the other. Discrepancies between our results and those of other workers are discussed.

Allosteric Regulation↗