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PubMed2004

Identification of CRALBP ligand interactions by photoaffinity labeling, hydrogen/deuterium exchange, and structural modeling.

Cellular retinaldehyde-binding protein (CRALBP) functions in the retinal pigment epithelium (RPE) as an acceptor of 11-cis-retinol in the isomerization step of the rod visual cycle and as a substrate carrier for 11-cis-retinol dehydrogenase. Toward a better understanding of CRALBP function, the ligand binding cavity in human recombinant CRALBP (rCRALBP) was characterized by photoaffinity labeling with 3-diazo-4-keto-11-cis-retinal and by high resolution mass spectrometric topological analyses. Eight photoaffinity-modified residues were identified in rCRALBP by liquid chromatography tandem mass spectrometry, including Tyr(179), Phe(197), Cys(198), Met(208), Lys(221), Met(222), Val(223), and Met(225). Multiple different adduct masses were found on the photolabeled residues, and the molecular identity of each modification remains unknown. Supporting the specificity of photo-labeling, 50% of the modified residues have been associate with retinoid interactions by independent analyses. In addition, topological analysis of apo- and holo-rCRALBP by hydrogen/deuterium exchange and mass spectrometry demonstrated residues 198-255 incorporate significantly less deuterium when the retinoid binding pocket is occupied with 11-cis-retinal. This hydrophobic region encompasses all but one of the photo-labeled residues. A structural model of CRALBP ligand binding domain was constructed based on the crystal structures of three homologues in the CRAL-TRIO family of lipid-binding proteins. In the model, all of the photolabeled residues line the ligand binding cavity except Met(208), which appears to reside in a flexible loop at the entrance/exit of the ligand cavity. Overall, the results expand to 12 the number of residues proposed to interact with ligand and provide further insight into CRALBP ligand and protein interactions.

Amino Acid Sequence↗

PubMed1993

AIDS anxieties of adolescents: determinants of "state" and "trait" anxiety dimensions in a linear structural model.

This study presents the effects of general psychologic characteristics on acquired immunodeficiency syndrome (AIDS) anxieties and sexual behaviour of adolescents. To this end, data were collected in a complex interview and subsequently subjected to a linear structural model analysis. The questioned adolescents were divided into one representative group (n = 256) and a second group who had participated in a voluntary human immunodeficiency virus (HIV) antibody test (n = 45). AIDS anxieties have to be divided into two independent dimensions: first, a relatively stable feeling of AIDS anxiety (trait anxiety) and second, a manifest personal anxiety toward AIDS experienced in a concrete situation (state anxiety). A principal component analysis of the primary data brought forth four variables described as depression/general anxiety, extent of phobic anxieties, compulsion, and tendency to self-consciousness. The present study reveals that the AIDS trait anxiety is more pronounced among those subjects who are not well informed about AIDS, who tend to phobic anxieties, and who observe themselves in a particularly intensive manner. The AIDS state anxiety however, is stronger among subjects who are well informed about AIDS, have sexual experience, and observe themselves intensively. Among the participants who took part in the HIV test, there were more individuals with a higher manifest AIDS anxiety and stronger tendency to depression. The percentage of adolescents who were indeed exposed to a possible risk of getting infected was relatively low. Generally speaking, those young people who are depressed, anxious, and sexually active agreed more easily to take the test than young people with a pronounced phobia toward the risk of infection and less sexual experience. As a conclusion, we can state that those adolescents with less sexual experience tend to externalize their general sexual anxieties in the form of concrete AIDS anxieties.

Acquired Immunodeficiency Syndrome↗

PubMed1976

A data structure model for a health information system.

The Ministry of Health and Environmental Control of Berlin is developing a Health Information System (HIS) on the basis of a multi-satellite network system, comprising a central, regional, local and functional unit level. The main part of this paper describes the conceptual structure of the Common Data Base (CDB) of HIS with special regard to the patient-oriented medical information originating from the various institutions of the health care system. This structure comprises the following five levels: 1. PATIENT 2. PROBLEM 3. CASE 4. EVENT 5. ACT Each of the levels represents a node in the structure model. A node is an entity with a set of "local properties" being specified for each level, referring to selected data on inferior levels. The structures of these five levels are described in detail. In the last part, so-called "data-manipulation procedures" are treated. These are descriptions covering any data manipulation and represent the basis of data integrity through system controlled transaction with the data base.

Berlin↗

PubMed1999

A test of the structural model of initiation of dieting among adolescent girls.

This article reports alternative findings from a pilot study to those presented recently (Strong GF, Huon KG. J. Psychosom. Res., 1998; 44:315-326) in regard to the proposed model of sociopsychological processes involved in the initiation of dieting among young adolescent girls. One hundred thirteen female high school pupils completed a battery of questionnaires that assessed dieting status, dietary restraint, autonomous functioning, skill-related functioning, social influence, and family functioning. The results indicate that family functioning predicts dietary restraint but that this effect is mediated by peer influence to diet. Furthermore, family functioning was associated with autonomous functioning, suggesting that this relationship should be pursued in a future test of the model. This pattern of results is different from an earlier test of the model, which indicated only a parental influence on dieting status. The results confirm that peer influences should be retained as a causal factor in a reformulated structural model.

Adolescent↗

PubMed2002

A dynamic structural model for estrogen receptor-alpha activation by ligands, emphasizing the role of interactions between distant A and E domains.

The functional interplay between different domains of estrogen receptor-alpha (ERalpha, NR3A1) is responsible for the overall properties of the full-length protein. We previously identified an interaction between the N-terminal A and C-terminal domains, which we demonstrate here to repress ligand-independent transactivation and transrepression abilities of ERalpha. Using targeted mutations based on ERalpha structural models, we determine the basis for this interaction that defines a regulatory interplay between ERalpha A domain, corepressors, and ERalpha Helix 12 for binding to the same C-terminal surface. We propose a dynamic model where binding of different ligands influences the A/D-F domain interaction and results in specific functional outcomes. This model gives insights into the dynamic properties of full-length ERalpha and into the structure of unliganded ERalpha.

Amino Acid Sequence↗

PubMed1998

Structural model of Dex protein from Penicillium minioluteum and its implications in the mechanism of catalysis.

The DEX gene encodes an extracellular dextranase (EC 3.2.1.11); this enzyme hydrolyzes the alpha(1,6) glucosidic bond contained in dextran to release small isomaltosaccharides. Sequence analysis has revealed only one homologous sequence, CB-8 protein, from Arthrobacter sp., with 30% sequence identity. The secondary structure prediction for Dex was corroborated by circular dichroism measurements. To explore the possibility that Dex protein might adopt a fold similar to any known structure, we conducted a threading search of a three-dimensional structure database. This search revealed that the Dex sequence is compatible with the galactose oxidase/methanol dehydrogenase/sialidase fold. A structural model of Dex based on these results is physically and biologically plausible and leads to testable predictions, including the prediction that Asp246 and Glu299 might be catalytic residues. Also, according to this model the Dex enzyme has a mechanism of hydrolysis with net inversion of anomeric configuration.

Amino Acid Sequence↗

PubMed2005

Synechocystis ferredoxin/ferredoxin-NADP(+)-reductase/NADP+ complex: Structural model obtained by NMR-restrained docking.

Ferredoxin (Fd) and ferredoxin-NADP(+)-reductase (FNR) are two terminal physiological partners of the photosynthetic electron transport chain. Based on a nuclear magnetic resonance (NMR)-restrained-docking approach, two alternative structural models of the Fd-FNR complex in the presence of NADP+ are proposed. The protein docking simulations were performed with the software BiGGER. NMR titration revealed a 1:1 stoichiometry for the complex and allowed the mapping of the interacting residues at the surface of Fd. The NMR chemical shifts were encoded into distance constraints and used with theoretically calculated electronic coupling between the redox cofactors to propose experimentally validated docked complexes.

Amino Acid Sequence↗

PubMed2002

New structure model for the GaAs(001)-c(4x4) surface.

The surface structure of the As-stabilized GaAs(001)-c(4 x 4) surface has been studied. We show that the seemingly established three As-dimer model is incompatible with experimental data and propose here a new structure model which has three Ga-As dimers per c(4 x 4) unit cell. This mixed dimer model, confirmed by the rocking-curve analysis of reflection high-energy electron diffraction and first-principles calculations, resolves disagreements in the interpretation of several previous experiments. A good agreement between the observed scanning tunneling microscopy image and the simulated one further confirms the newly proposed model.

Journal Article↗

PubMed1998

Probing the structure of the human Ca2+- and Zn2+-binding protein S100A3: spectroscopic investigations of its transition metal ion complexes, and three-dimensional structural model.

A large-scale procedure was developed for the anaerobic purification of the human recombinant Ca2+- and Zn2+-binding protein S100A3 for spectroscopic studies. S100A3 eluted as a non-covalently bound dimer (20.8 kDa). It contained 7.5+/-0.1 free thiol groups/monomer, and bound Ca2+ with a Kd of approximately 4 mM, which corresponds to a tenfold increase in affinity compared to the aerobically purified protein. The transition metal ions Co2+, Zn2+ and Cd2+ were used as spectroscopic probes to investigate the role of the 10 cysteine residues per monomer S100A3 in metal binding. Spectrophotometric titrations suggest the formation of dinuclear thiolate-bridged clusters consisting of a Me2+(S(Cys))4 and a Me2+(S(Cys))3(N(His)) site as described for zinc finger proteins. A three-dimensional structural model of S100A3 was proposed on the basis of the NMR structure of the structurally related rabbit S100A6 protein, and taking into account the structural influence of cysteine residues.

Amino Acid Sequence↗

PubMed1990

Phylogenetic and biochemical evidence for a secondary structure model of a small cytoplasmic RNA from Bacilli.

Small cytoplasmic RNA (scRNA; 271 nucleotides) is an abundant, stable RNA identified in the Gram-positive eubacterium Bacillus subtilis. Several findings suggest an important role of scRNA in protein biosynthesis: it shares structural and biochemical features with the Escherichia coli 4.5S RNA (114 nucleotides), a molecule known to be involved in this process, and it can complement the essential function of 4.5S RNA in vivo. The common apical hairpin motif of scRNA and 4.5S RNA also exists in eukaryotic 7SL RNA, the RNA component of the signal recognition particle. To elucidate the higher-order structure of scRNA, we have combined a phylogenetic approach with a biochemical one. The sequence of scRNA from a thermophilic relative of B. subtilis, Bacillus stearothermophilus, was determined and compared with the B. subtilis scRNA. In addition, the solution structure of B. stearothermophilus scRNA was probed with single- and double-strand-specific nucleases. Both types of analysis support a secondary structure model for scRNA that strongly resembles 4.5S RNA and respective parts of 7SL RNA. The results provide further evidence for the suggestion of a functional relationship between these RNAs.

Bacillus subtilis↗

PubMedDate not supplied

A structural model for the Escherichia coli DnaB helicase based on electron microscopy data.

The DnaB protein is the major replicative DNA helicase in Escherichia coli. It hydrolyzes ATP to promote its translocation in the 5' to 3' direction on single-stranded DNA templates, facilitating the separation of strands of duplex DNA in its path. This places it on the lagging strands at replication forks during chromosomal DNA replication. Electron microscopic images of negatively stained DnaB protein have been studied and processed to produce a three-dimensional reconstruction of the protein oligomer at 2.7 nm resolution. While it is known that the native protein is a complex of six identical 52-kDa subunits, the specimen shows threefold rather than sixfold symmetry, with three outer stain-excluding regions surrounding another six, more massive, lobules. There is a channel through the particle that appears fully open on both sides. Based on these results, a structural model for the oligomer is presented, and functional implications are considered.

Bacterial Proteins↗

PubMed1997

A structural model of the human thrombopoietin receptor complex.

Thrombopoietin (TPO) is a glycoprotein hormone that regulates red blood cell production. Presented here is a modeling study of the extracellular region of the human thrombopoietin receptor complex, in particular the TPO-receptor interface. The models were developed from structural homology to other cytokines and their receptors. Experimental evidence suggests that the receptor is homodimeric and it was modeled accordingly. Key interactions are shown that correlate with previous cytokine receptor complexes, and the pattern of cysteine bonding (Cys7-Cys151 and Cys29-Cys85) agrees with that experimentally determined for thrombopoietin. These models pave the way for possible mutagenesis experimentation and the design of (ant)agonists.

Amino Acid Sequence↗

PubMed1998

Implementing the differentiated pay structure model. Process and outcomes.

OBJECTIVE: A salaried Differentiated Pay Structure (DPS) model based on the work of Dr. Virginia Cleland was tested on two units. The project objectives were to: 1) create a budget-neutral compensation distinction for different competencies and educational levels; 2) evaluate the effect of the new salaried model on unit costs and pay; 3) determine the effect of the DPS model on job satisfaction, organizational commitment, and anticipated turnover; and 4) assess the impact of professional commitment, professional practice climate, perception of staffing adequacy, and dispositional optimism on job satisfaction, organizational commitment, and anticipated turnover. BACKGROUND: Although there has been long-standing interest in salaried models and reward methodologies, there is a dearth of systematic research associated with specific compensation models. METHODS: A quasi-experimental, non-equivalent control group design was used to examine the effects of the DPS model. RESULTS: Findings demonstrated that nurses were paid more under the DPS model, and that they were paid for more hours than they actually worked (N = 68). No difference in job satisfaction was found between experimental and control groups. For all nurses (N = 232) dispositional optimism was associated with all job satisfaction subscales except pay. Organizational commitment, professional commitment, professional practice climate, and staffing adequacy were also correlated with job satisfaction, perceptions of care quality and anticipated turnover. Older nurses who had worked longer in nursing, and who had more tenure were less satisfied with their coworkers and care quality. CONCLUSION: Further longitudinal research with larger experimental samples is required in order to fully understand the effects of the DPS model in nursing.

Adult↗

PubMedDate not supplied

A chronomorphological structural model of rat thyroid gland.

Circadian rhythmicity of the structural morphometric model of thyroid has been studied in 36 Wistar rats kept in LD 12:12. The parameters evaluated are: a. the volume fraction occupied by: 1. follicle epithelium, 2. colloid, 3. interstitium at 6 time points in 24h; b. the follicle size distribution; c. the number of follicles per unit tissue volume. The circadian rhythms of mean follicular diameter and of follicular cavity mean diameter have been demonstrated (p less than 0.03 and p less than 0.01 respectively) and show overlapping acrophases of -120 degrees (-64 degrees/-176 degrees) and -108 degrees (-99 degrees/-116 degrees). The synchronization between rhythms, shown for mean follicular diameter and for follicular cavity mean diameter, suggests a rhythmical pulsation of the whole follicle, while the thickness of the follicular epithelium does not undergo a statistically significant periodic variation.

Animals↗

PubMed2001

Structural models of human apolipoprotein A-I: a critical analysis and review.

Human apolipoprotein (apo) A-I has been the subject of intense investigation because of its well-documented anti-atherogenic properties. About 70% of the protein found in high density lipoprotein complexes is apo A-I, a molecule that contains a series of highly homologous amphipathic alpha-helices. A number of significant experimental observations have allowed increasing sophisticated structural models for both the lipid-bound and the lipid-free forms of the apo A-I molecule to be tested critically. It seems clear, for example, that interactions between amphipathic domains in apo A-I may be crucial to understanding the dynamic nature of the molecule and the pathways by which the lipid-free molecule binds to lipid, both in a discoidal and a spherical particle. The state of the art of these structural studies is discussed and placed in context with current models and concepts of the physiological role of apo A-I and high-density lipoprotein in atherosclerosis and lipid metabolism.

Amino Acid Sequence↗

PubMed1978

A structural model of cholinergic synaptic vesicles from the electric organ of Torpedo marmorata deduced from density measurements at different osmotic pressures.

Density measurements made on cholinergic synaptic vesicles from the electric organs of Torpedo marmorata at different osmotic pressures are consistent with the following structural model of the vesicle. The particle behaves like a sphere 80-100 nm in diameter bounded by a semi-permeable membrane. The bulk of its soluble constituents are in true solution at physiological osmolalities. The limiting membrane is approximately 4-5 nm thick, suggesting that it contains large areas of phospholipid bilayer exposed to its bathing medium. The limiting membrane takes up about 26% (v/v) of the particle, a further 34% (v/v) of which is osmotically active water and 31% (v/v) hydrated core material at 800 mosmol/1. The buoyant density of the membrane is 1.132 g . cm-3. The density of the hydrated core material is approximately 1.05 g . cm-3. The membrane is selectively permeable to small molecules when subjected to hypo-osmotic stress. It is proposed that this occurs by the formation of small transient pores in the lipid bilayer of the membrane, which are induced by stretching caused by the osmotic pressure change.

Acetylcholine↗

PubMed2000

Structural model of the Fe-hydrogenase/cytochrome c553 complex combining transverse relaxation-optimized spectroscopy experiments and soft docking calculations.

Fe-hydrogenase is a 54-kDa iron-sulfur enzyme essential for hydrogen cycling in sulfate-reducing bacteria. The x-ray structure of Desulfovibrio desulfuricans Fe-hydrogenase has recently been solved, but structural information on the recognition of its redox partners is essential to understand the structure-function relationships of the enzyme. In the present work, we have obtained a structural model of the complex of Fe-hydrogenase with its redox partner, the cytochrome c(553), combining docking calculations and NMR experiments. The putative models of the complex demonstrate that the small subunit of the hydrogenase has an important role in the complex formation with the redox partner; 50% of the interacting site on the hydrogenase involves the small subunit. The closest contact between the redox centers is observed between Cys-38, a ligand of the distal cluster of the hydrogenase and Cys-10, a ligand of the heme in the cytochrome. The electron pathway from the distal cluster of the Fe-hydrogenase to the heme of cytochrome c(553) was investigated using the software Greenpath and indicates that the observed cysteine/cysteine contact has an essential role. The spatial arrangement of the residues on the interface of the complex is very similar to that already described in the ferredoxin-cytochrome c(553) complex, which therefore, is a very good model for the interacting domain of the Fe-hydrogenase-cytochrome c(553).

Cytochrome c Group↗

PubMed2006

Happiness and congruence in older adulthood: a structural model of life satisfaction.

The purpose of this study was to determine how health impairment, socioeconomic status, and social support relate to life satisfaction in later life. Using data from a sample of 320 older adults from The Georgia Centenarian Study, we constructed a structural model of life satisfaction. LISREL analysis was performed to test a two-factor model that included Happiness and Congruence and to determine the relationship of health impairment, socioeconomic status (SES), and social support to Happiness and Congruence, two measures of the Life Satisfaction Index-A (LSI-A). Data were found to provide a satisfactory fit of the model (GFI = 0.94; AFGI = 0.91). Social support and SES were found to have direct effects on health impairment. Health impairment was a key predictor and mediating variable of Happiness and Congruence. Findings also support a relationship between social resources and subjective well-being in later life. In particular, the association between social resources and life satisfaction was mediated through health impairment. These findings offer understanding relative to how health and social resources influence past and present assessments of subjective well-being among the elderly.

Adult↗