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PubMedDate not supplied

[Structural instability of co-integrates formed during interaction of plasmid R57 with pB322 and RP1. Possible role of IS1 element in the degradation of co-integrates].

The conjugative plasmid R57 determines resistance to ampicillin and chloramphenicol. Earlier it was shown that R57 encodes site-specific recA-independent recombinase, which acts in cis and resolves IS1-mediated cointegrates arising in the Escherichia coli recA cells between R57 and pBR322. In the present work the properties of the cointegrates between R57 and pBR322 or RP1 arising in the E. coli rec+ strains were studied. It was found that the cointegrates between R57 and pBR322, obtained by mating of the respective biplasmid donors of E. coli rec+ and the rec+ recipients, lost as a result of deletion a large DNA segment of R57 containing determinant Cmr. The resulting hybrid replicons preserved determinants Apr and Tcr of pBR322 and the R57 conjugative properties and were structurally identical. By using plasmid RP1ts12, which is temperature-sensitive in replication, it was demonstrated that in cells rec+ the cointegrates between R57 and RP1 are extremely unstable. On storage they undergo structural degradation mainly affecting the RP1 replicon. The degradation products of the hydrid complex had lost their RP1 genes but preserved the R57 functional determinants. For elucidation of the observed phenomena the properties of the IS1-mediated cointegrates between pBR322:Tn9 and plasmid pBR3.1--deletion derivative of RP1 were studied. It was found that insertion of IS1 sometimes resulted in formation of unstable cointegrates capable of resolving and loosing determinant Cmr with a high frequency. It was suggested that IS1 encodes the site-specific recombinase responsible for resolution of the IS1-mediated cointegrates and deletion generation. Expression of this recombinase appears to be dependent on structure of the insertion sites. The possible role of IS1 and recombinase encoded by it in resolution and structural instability of the cointegrates between R57 and pBR322 or RP1 is discussed.

Chromosome Mapping↗

PubMed1997

Adenosine-dopamine receptor-receptor interactions as an integrative mechanism in the basal ganglia.

Increasing evidence suggests that antagonistic interactions between specific subtypes of adenosine and dopamine receptors in the basal ganglia are involved in the motor depressant effects of adenosine receptor agonists and the motor stimulant effects of adenosine receptor antagonists, such as caffeine. The GABAergic striatopallidal neurons are regulated by interacting adenosine A2A and dopamine D2 receptors. On the other hand, the GABAergic striatonigral and striatoentopeduncular neurons seem to be regulated by interacting adenosine A1 and dopamine D1 receptors. Furthermore, behavioural studies have revealed interactions between adenosine A2A and dopamine D1 receptors that occur at the network level. These adenosine-dopamine receptor-receptor interactions might offer new therapeutic leads for basal ganglia disorders.

Animals↗

PubMed1992

Teaching social skills to students with autism to increase peer interactions in an integrated first-grade classroom.

We investigated the use of social skills groups to facilitate increased social interactions for students with autism and their nonhandicapped peers in an integrated first-grade classroom. Social skills groups consisted of training students and peers in initiating, responding, and keeping interactions going; greeting others and conversing on a variety of topics; giving and accepting compliments; taking turns and sharing; asking for help and helping others; and including others in activities. Training occurred during the first 10 min of 20-min play groups, four times per week. Using a multiple baseline across subjects design, results demonstrated increases in the frequency of, time engaged in, and duration of social interactions, as well as the responsivity of students and peers to each other. Results were maintained when students were monitored and given feedback on social performance in play groups and during follow-up.

Autistic Disorder↗

PubMed1996

Immediate effects of mainstreamed settings on the social interactions and social integration of preschool children.

The immediate effects of mainstreamed and specialized settings on the peer interactions of preschool children with and without developmental delays were examined. Mainstreamed and specialized playgroups were established involving unacquainted peers and using a methodology that ensured appropriate matching of child and family characteristics. For each 2-week playgroup, the social and play interactions of each child were observed during a designated free-play period. Peer sociometric ratings also were obtained. Results indicated higher levels of peer interactions in mainstreamed settings for both typically developing children and children with developmental delays. The immediate impact of mainstreamed settings appeared to be attributed to the social demands and higher interaction levels of the former group. Children with developmental delays were not fully accepted nor totally socially integrated based on sociometric measures and behavioral indices of peer preferences. Implications of these findings for developing intervention programs to maximize children's peer-related social competence was discussed.

Child, Preschool↗

PubMed2025

TRAIT: A Comprehensive Database for T-cell Receptor-antigen Interactions.

Comprehensive and integrated resources on interactions between T-cell receptors (TCRs) and antigens are still lacking for adoptive T-cell-based immunotherapies, highlighting a significant gap that must be addressed to fully understand the mechanisms of antigen recognition by T cells. In this study, we present the T-cell receptor-antigen interaction database (TRAIT), a comprehensive database that profiles the interactions between TCRs and antigens. TRAIT stands out due to its comprehensive description of TCR-antigen interactions by integrating sequences, structures, and affinities. It provides millions of experimentally validated TCR-antigen pairs, resulting in an exhaustive landscape of antigen-specific TCRs. Notably, TRAIT emphasizes single-cell omics as a major reliable data source for TCR-antigen interactions and includes millions of reliable non-interactive TCRs. Additionally, it thoroughly demonstrates the interactions between mutations of TCRs and antigens, thereby benefiting affinity optimization of engineered TCRs as well as vaccine design. TCRs on clinical trials are innovatively provided. With the significant efforts made toward elucidating the complex interactions between TCRs and antigens, TRAIT is expected to ultimately contribute superior algorithms and substantial advancements in the field of T-cell-based immunotherapies. TRAIT is freely accessible at https://pgx.zju.edu.cn/traitdb.

Receptors, Antigen, T-Cell↗

PubMed1991

Integrated fluid handling system for biomolecular interaction analysis.

An integrated fluid handling system used for multichannel biomolecular interaction analysis is described. Reactions between biological molecules are monitored in real time by measuring changes in the angular position where surface plasmon resonance occurs at a biospecific active surface. The adsorption efficiency of the analyte onto the biospecific active surface is up to approximately 3%, due to the low channel height, 50 microns, in the flow cell. When a large part of the total biospecific active surface for surface plasmon resonance probing (approximately 0.15 mm2) is used, the sensitivity is high. Sample sizes in the order of 1-50 microL can be injected. The sample zone dispersion is minimized by the low dead volume in the system (approximately 0.4 microL) accomplished by using integrated sample loops and thin conduits. An asset of this integration is the low reagent consumption. The sensor chip with the biospecific active surface is reusable and easily exchanged. Experimental results obtained with a theophylline monoclonal antibody as the analyte are compared with a theoretical model. The standard deviation for the repeatability is approximately 5% typically with 50 microL of 250 pM analyte, and the assay time is 10 min. The detection limit is approximately 10 pg of the analyte on the probed spot of the surface. Possible improvements of the sensitivity and detection limit are discussed.

Antibodies, Monoclonal↗

PubMed1998

A graphical user interaction model for integrating complex clinical applications: a pilot study.

We have developed and implemented a multi-faceted, graphical user interaction model for an advanced clinical information system. This paper describes a classification scheme for applications used by clinicians in their daily work, discusses the way clinicians interact with these applications, and the issues that arise during these user interactions. Through its emphasis on support for application interoperation, the graphical user interface that implements the model presents a single, consistent, context to the user, and thereby helps maintain patient safety and ensure ease of use.

Computer Graphics↗

PubMed1988

Integration host factor interacts with the DNA replication enhancer of filamentous phage f1.

We present data which show that the Escherichia coli integration host factor (IHF) is an activator of phage f1 DNA replication. Phage f1 poorly infects bacterial strains lacking IHF because IHF is required for efficient expression of F-pili, the receptor for f1 phage. However, when F- strains are transfected with f1 DNA the phage replicates in IHF mutants (himA, himD, or himA himD) at a rate of only 3% of that in wild-type bacteria. A plasmid dependent on the f1 replicon fails to transform IHF mutants. By gel retardation analysis, we show that IHF specifically binds to the origin of replication. DNase I "footprinting" experiments demonstrate that IHF binds to multiple sites within the replication enhancer sequence, a cis-acting, A + T-rich sequence that potentiates f1 DNA replication. Moreover, the effect of IHF mutation on f1 growth is suppressed by initiator protein (f1 gene II) mutations that restore efficient replication from origins that lack a functional replication enhancer sequence. This genetic evidence supports the conclusion that the replication enhancer sequence is the site of action of IHF.

Bacterial Proteins↗

PubMed1991

Genetic analysis of Escherichia coli integration host factor interactions with its bacteriophage lambda H' recognition site.

The bacteriophage P22-based challenge phage system was used to study the binding of integration host factor (IHF) to its H' recognition site in the attP region of bacteriophage lambda. We constructed challenge phages that carried H' inserts in both orientations within the P22 Pant promoter, which is required for antirepressor synthesis. We found that IHF repressed expression of Pant from either challenge phage when expressed from an inducible Ptac promoter on a plasmid vector. Mutants containing changes in the H' inserts that decrease or eliminate IHF binding were isolated by selecting challenge phages that could synthesize antirepressor in the presence of IHF. Sequence analysis of 31 mutants showed that most changes were base pair substitutions within the H' insert. Approximately one-half of the mutants contained substitutions that changed base pairs that are part of the IHF consensus binding site; mutants were isolated that contained substitutions at six of the nine base pairs of the consensus site. Other mutants contained changes at base pairs between the two subdeterminants of the H' site, at positions that are not specified in the consensus sequence, and in the dA + dT-rich region that flanks the consensus region of the site. Taken together, these results show that single-base-pair changes at positions outside of the proposed consensus bases can weaken or drastically disrupt IHF binding to the mutated site.

Bacterial Proteins↗

PubMed1994

Stabilization of platelet-fibrinogen interactions is an integral property of the glycoprotein IIb-IIIa complex.

Fibrinogen binding to platelets is multiphasic and culminates in the stabilization of platelet-fibrinogen interactions characterized by the resistance of bound fibrinogen to dissociation by ethylenediaminetetraacetic acid (EDTA) or excess unlabeled fibrinogen. Controversy exists, however, with regard to the exclusive role of the glycoprotein IIb-IIIa (GPIIb-IIIa) complex in this process. Thus the reversibility of fibrinogen binding to purified GPIIb-IIIa and GPIIb-IIIa activated by a monoclonal antibody (D3) on otherwise resting platelets was examined. GPIIb-IIIa was isolated by affinity chromatography on concanavalin A followed by gel filtration on Sephacryl S-300 and immobilized directly on plastic microtiter wells or immunocaptured by immobilized anti-GPIIb or GPIIIa antibodies. The extent of GPIIb-IIIa deposition, 0.14 to 0.27 pmol/well, was determined by using a monoclonal, anti-GPIIb-IIIa antibody (10E5). Maximum fibrinogen binding occurred after 60 minutes at 22 degrees C in the presence of 300 micrograms/ml fibrinogen, when 0.014 to 0.030 pmol fibrinogen bound per well. Assuming a 1:1 relationship between fibrinogen binding and GPIIb-IIIa occupancy, these data suggest that approximately 10% to 20% of immobilized GPIIb-IIIa was in an active confirmation. After 60 minutes, 65% +/- 13% of bound fibrinogen was resistant to dissociation by excess unlabeled fibrinogen, and 53% +/- 24% failed to dissociate with 10 mmol/L EDTA. Fibrinogen fragment D1 also bound irreversibly to immobilized GPIIb-IIIa (52% +/- 18%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗

PubMed1986

An integrated model for the interaction of muscle relaxants with their antagonists.

An integrated model describing the interaction of nondepolarizing neuromuscular blocking agents with reversible anticholinesterase agents is derived and compared with a naive model using experimental data obtained from four anesthetized dogs. Three consecutive but separate steady-state d-tubocurarine blocks (approximately 50, 70, and 90%) were induced in each of the four dogs and reversed by short edrophonium infusions. Edrophonium arterial concentrations and twitch tension of the anterior tibialis muscle were measured. Both the integrated and the naive model were fit to the twitch tension data using a model with a hypothetical "effect" compartment. The integrated model consistently fit the twitch tension data better than the naive model; the sum of squared deviations was lower by 46, 45, 87, and 69%, respectively, with the integrated model than with the naive model. Also, in contrast to the naive model, the integrated model is capable of describing the interaction of the anticholinesterase agent and the neuromuscular blocking agent when the concentration of either varies with time.

Animals↗

PubMed1979

Integral membrane protein interaction with Triton cytoskeletons of erythrocytes.

The organization of erythrocyte membrane lipids and proteins has been studied following the release of cytoplasmic components with the non-ionic detergent Triton X-100. After detergent extraction, a detergent-resistant complex called the erythrocyte cytoskeleton is separated from detergent, solubilized lipid and protein by sucrose buoyant density sedimentation. In cytoskeletons prepared under isotonic conditions all of the major erythrocyte membrane proteins are retained except for the integral protein, glycophorin, which is quantitatively solubilized and another integral glycoprotein, band 3, which is only 60% removed. When cytoskeletons are prepared in hypertonic KCl solutions, band 3 is fully solubilized along with bands 2.1 and 4.2 and several minor components. The resulting cytoskeletons have the same morphology as those prepared in isotonic buffer but they are composed of only three major peripheral proteins, spectrin, actin and band 4.1. We have designated this peripheral protein complex the 'shell' of the erythrocyte membrane, and have shown that the attachment of band 3 to the shell satisfies the criteria for a specific interaction. Although Triton did affect erythrocyte shape, cytoskeleton lipid content and the activity of membrane proteases, there was no indication that Triton altered the attachment of band 3 to the shell. We suggest that band 3 attaches to the shell as part of a ternary complex of bands 2.1, 3 and 4.2.

Erythrocyte Membrane↗

PubMed1988

Interaction of amphiphiles with integral membrane proteins. II. A simple, minimal model for the nonspecific interaction of amphiphiles with the anion exchanger of the erythrocyte membrane.

In a previous paper we have reported on the structural perturbation of the erythrocyte membrane anion exchanger by a regular series of model amphiphiles, as shown by differential scanning calorimetry (Gruber, H.J. and Low, P.S., Biochim. Biophys. Acta, preceding article). Now the data are interpreted by a model in which the effects of amphiphile structure upon buffer-membrane partitioning are well separated from the dependence of the intrinsic potencies of membrane-bound amphiphiles upon amphiphile structure. The buffer-membrane partitioning situation was demonstrated to regularly change between extremes within a series of homologous amphiphiles, i.e. from a negligible to a predominant fraction of total amphiphile in the sample residing in the membrane. Based upon this demonstration a large number of reports on the chain length dependence of apparent potency could be reinterpreted in terms of chain length profiles of intrinsic potency, allowing for a comparison of the responses of various membrane proteins to homologous series of amphiphiles. The response patterns for chain length variation could be divided into three distinct classes: the intrinsic potency (i) can be independent of chain length over a very wide range of length, (ii) it can be rather independent up to a critical length where a sudden cut-off in potency occurs, or (iii) it can drop monotonically over a wide range of chain length. The intrinsic potency values of saturated fatty acids in destabilizing the anion exchanger were interpreted by very simple assumptions: only direct interactions between amphiphiles and target proteins and a simple amphiphile partition equilibrium between a pool of equivalent low affinity sites on the protein and the bulk lipid matrix. The observed monotonic decay of the intrinsic potency of saturated fatty acids with increasing chain length from C8 to C20 was translated into a constant increment of free energy by which each additional CH2 favors the transfer away from sites on the protein towards the bulk lipid matrix. Arguments were presented suggesting that the direct interaction between amphiphiles and target protein is completely nonspecific for alkyl chain length while the residual specificity for shorter over longer amphiphiles is due to the higher tendency of longer chains to preferentially bind in the bulk lipid matrix. Thus a completely new role of the lipid as a competitor, rather than a mediator, was postulated.

Cell Membrane↗

PubMed1996

Interaction between an integral protein of the nuclear envelope inner membrane and human chromodomain proteins homologous to Drosophila HP1.

At the nuclear envelope in higher eukaryotic cells, the nuclear lamina and the heterochromatin are adjacent to the inner nuclear membrane, and their attachment is presumably mediated by integral membrane proteins. In a yeast two-hybrid screen, the nucleoplasmic domain of lamin B receptor (LBR), an integral protein of the inner nuclear membrane, associated with two human polypeptides homologous to Drosophila HP1, a heterochromatin protein involved in position-effect variegation. LBR fusion proteins bound to HP1 proteins synthesized by in vitro translation and present in cell lysates. Antibodies against LBR also co-immunoprecipitated HP1 proteins from cell extracts. LBR can interact with chromodomain proteins that are highly conserved in eukaryotic species and may function in the attachment of heterochromatin to the inner nuclear membrane in cells.

Amino Acid Sequence↗

PubMed1982

Role of membrane integrity and cation interaction for heart sarcolemmal adenylate cyclase and Na+-K+ ATPase.

The adenylate cyclase and Na+ -K+ ATPase activities decreased on storage at 4 degrees C as well as on freezing and thawing of the rat heart sarcolemma. Treatment of the sarcolemmal fraction with phospholipase C and trypsin also depressed the adenylate cyclase and Na+ -K+ ATPase activities; the Na+ -K+ ATPase was more sensitive to these treatments than the adenylate cyclase. When the sarcolemmal enzyme activities were determined in the presence of different concentrations of some cations the adenylate cyclase activity was enhanced and the Na+ -K+ ATPase activity was depressed by monovalent cations (Na+, K+, Rb+, Cs+, Li+, and NH+4). Divalent cations such as Sr2+, Ba2+, Co2+, and Mn2+ had biphasic or no effects on the adenylate cyclase activity but inhibited the Na+ -K+ ATPase activity. Although Ca2+, Ni2+, Cd2+, Cu2+, Hg2+, and Zn2+ depressed both Na+ -K+ ATPase and adenylate cyclase activities, the degree of inhibition of these enzymes was different. These results reveal the role of membrane integrity for full expression of the adenylate cyclase and Na+ -K+ ATPase activities, whereas both monovalent and divalent cations appear to regulate sarcolemma-bound enzyme activities.

Adenylyl Cyclases↗

PubMedDate not supplied

Cooperative and competitive spatial interactions in motion integration.

Recovering the velocity of objects moving in the visual field requires both the integration and segmentation of local neuronal responses elicited by moving stimuli in primary visual cortex. Herein, we investigate the effects of the contrast, density, spatial proximity, spatial frequency, and spatial configuration of component motions on these complementary processes. Measuring the ability of human observers to discriminate the global direction of motion displays composed of spatially distributed patches of drifting gratings whose motion is locally ambiguous, we provide psychophysical evidence that linking component motion across space is facilitated at low contrast and high patch density. Furthermore, direction discrimination depends on the spatial frequency of component gratings and is more accurate for spatial configurations that contain "virtual" L junctions as compared to configurations composed of "virtual" T junctions. We suggest that the conditions yielding global motion coherence can be accounted for by the existence of anisotropic cooperative/competitive, contrast-dependent, long-range interactions among oriented direction-selective units. In addition, we bring evidence that motion segmentation processes rely upon the processing of moving local spatial discontinuities. The results are discussed in the light of recent psychophysical and physiological evidence that long-range excitatory and inhibitory interactions within primary visual cortex modulate perceptual linking.

Contrast Sensitivity↗

PubMed1990

Alterations in the p'R promoter of coliphage lambda modify both its activity and interaction with the integration host factor (IHF).

A limited number of deletion/insertions and a point mutation in the -35 region of the p'R promoter of phage lambda were examined and found to influence both transcription and its repression by the integration host factor (IHF). Positive effects on transcription (in the absence of IHF) are small (up to 1.4-fold) and are caused by a deletion-substitution upstream of the -35/ihf site. Up to three base changes in the -35 promoter element seem to be tolerated, with only a small negative effect on transcription. In some cases, effective transcription requires supercoiling of such mutant template. Since an ihf sequence overlaps the -35 region of p'R, IHF represses transcription. Repression is correlated with IHF binding and consequent DNA bending, as assessed by gel retardation experiments. Nine p'R mutants were tested for their IHF binding and repression; the results confirm the consensus sequence, 5'-W2WWWWN7WWWWCARNWN2TTR derived from the hydroxyl radical footprinting, where the bold letters indicate the IHF-protected bases and W is A or T, R is A or G and N represents A, T, G or C. Perhaps surprisingly, some mutations just upstream or downstream of this ihf sequence also affect IHF binding, as observed not only for the pR'/ihf but also for the att H' site of lambda. Supercoiling in some cases permits the IHF-mediated repression to be overcome, probably by increasing the RNA polymerase binding and/or decreasing the interaction with IHF. All our data are consistent with a model which assumes that IHF initially binds to one or two ihf contact points depending on preexisting DNA topology, bends DNA, and completes the remaining contacts while finally adjusting the DNA conformation to establish the best fit within the minor groove of the double helix. Effective IHF repression of transcription would thus depend on several factors, including: (1) the sequence, and (2) the initial conformation of the ihf site, together with (3) the capacity of IHF to compete with RNA polymerase for the overlapping binding sites.

Bacterial Proteins↗

PubMed1998

Protein subunit interactions and structural integrity of amyloidogenic transthyretins: evidence from electrospray mass spectrometry.

Wild-type and variant transthyretins form amyloid fibrils in two different diseases. The biologically active form of transthyretin is a tetramer but there is evidence that a monomeric species is the amyloidogenic intermediate. Using mass spectrometry we have developed an approach to monitor the proportions of monomer and tetramer in wild-type and variant transthyretins, and found a strong correlation between the instability of the tetramer in the gas phase and the amyloidogenicity of the protein variant. The presence of water molecules in the central channel has been found to be critical for maintaining intact the complex in the gas phase, with additional stability observed in the presence of excess thyroxine. The solution structure of monomeric transthyretin under fibril-forming conditions was studied using hydrogen exchange monitored by mass spectrometry. The results show that Val30Met transthyretin, the commonest amyloidogenic variant, exhibits loss of hydrogen exchange protection substantially more rapidly than the wild-type protein, suggesting partial unfolding of the beta-sheet structure. These results provide new insights into the correlation between tetramer stability and amyloidogenicity as well as supporting a possible route to fibril formation via transient unfolding of the transthyretin monomer.

Amyloid↗