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Biomedical subjects

G Wagner

Publications and source records attributed to G Wagner.

At least 199 records · Page 11Linked to original sources
PubMed1996

Phytochrome of the green alga Mougeotia: cDNA sequence, autoregulation and phylogenetic position.

A cDNA clone encoding phytochrome (apoprotein) of the zygnematophycean green alga Mougeotia scalaris has been isolated and sequenced. The clone consisted of 3372 bp, encoded 1124 amino acids, and showed strainspecific nucleotide exchanges for M. scalaris, originating from different habitats. No indication was found of multiple phytochrome genes in Mougeotia. The 5' non-coding region of the Mougeotia PHY cDNA harbours a striking stem-loop structure. Homologies with higher-plant phytochromes were 52-53% for PHYA and 57-59% for PHYB. Highest homology scores were found with lower-plant phytochromes, for example 67% for Selaginella (Lycopodiopsida), 64% for Physcomitrella (Bryopsida) and 73% for Mesotaenium (Zygnematophyceae). In an unrooted phylogenetic tree, the position of Mougeotia PHY appeared most distant to all other known PHYs. The amino acids Gly-Val in the chromophore-binding domain (-Arg-Gly-Val-His-Gly-Cys-) were characteristic of the zygnematophycean PHYs known to date. There was no indication of a transmembrane region in Mougeotia phytochrome in particular, but a carboxyl-terminal 16-mer three-fold repeat in both, Mougeotia and Mesotaenium PHYs may represent a microtubule-binding domain. Unexpected for a non-angiosperm phytochrome, its expression was autoregulated in Mougeotia in a red/far-red reversible manner: under Pr conditions, phytochrome mRNA levels were tenfold higher than under Pfr conditions.

Amino Acid Sequence↗
PubMed1996

The structural role of sugars in glycoproteins.

To date, high resolution X-ray structures of about 30 glycoproteins have been reported that provide some structural information on glycans. Four solution structures of glycoproteins have been described over the past three years. In all four of these cases, it was shown that glycosylation is stabilizing the glycoprotein structures, indicating that this may be a general glycan function.

Binding Sites↗
PubMed1996

Theory and practice of nuclear spin relaxation in proteins.

NMR relaxation experiments can provide information on overall and internal motions in proteins. This review consists of a concise report on the evolution of the theories for nuclear relaxation followed by an overview of mathematical models for internal motions in proteins. Next, the method of spectral density mapping with recent developments is reviewed. This is followed by a discussion of pulse sequences for relaxation experiments. Finally, we review recent studies correlating relaxation parameters, in particular spectral density functions, with structural features of proteins and with results of molecular dynamics simulations.

Enzymes↗
PubMed1996

Internalized homophobia in a sample of HIV+ gay men, and its relationship to psychological distress, coping, and illness progression.

The purpose of this study was to determine whether internalized homophobia is related to psychological distress and coping style and whether these relationships are moderated by illness stage. A sample of gay men, most of whom were HIV+, Caucasian, and well educated, were administered assessments at both baseline and 2-year follow-up, which allowed for the assessment of change over time in the context of HIV illness progression and to determine whether internalized homophobia predicts psychological distress and coping over time. Greater internalized homophobia at baseline, specifically among those who were HIV+ asymptomatic, predicted higher levels of distress at follow-up. In contrast, internalized homophobia had, at best, a weak association with coping. No relationship was found between illness stage and internalized homophobia, psychological distress, or coping. Mental health professionals working with HIV+ gay men may be more effective in targeting resources and interventions aimed at improving mental health and quality of life if they address issues related to internalized homophobia.

Adaptation, Psychological↗
PubMed1996

Selective binding of Ca2+, Zn2+, Cu2+ and K+ by the physodes of the green alga Mougeotia scalaris.

Cells of the zygnematophycean green alga Mougeotia contain numerous globules with polyphenolic matrix, which resemble physodes. In order to analyse the capability of this compartment to sequester various ions, trichomes of Mougeotia scalaris were either fixed for X-ray microanalysis simultaneously in 2% glutardialdehyde/1% OsO4 in phosphate buffers of different K+/Na(+)-ratios, or embedded directly (fresh material) in Nanoplast resin. In addition, fixed material was treated with potassium antimonate and Ca2+ localization was examined by electron microscopic cytochemistry. A Ca(2+)-depletion upon fixation at different K+/Na(+)-ratios resulted in selective uptake of potassium, but not sodium. Consistent with earlier findings, calcium-binding by the polyphenolic physode matrix does not depend merely on electric charge but also on the presence of protonated/deprotonated phenolic groups, together with ester-linked carbonyl oxygen, which seem to be good candidates for a co-ordinate type of calcium-binding. Nanoplast embedding turned out to be the most adequate and fastest preparation for X-ray microanalysis and, apart from retaining calcium, allowed the detection of zinc and copper inside the physodes.

Calcium↗
PubMed1996

Glucose-6-phosphate dehydrogenase deficiency mutations in Papua New Guinea.

We characterize the molecular basis of two G6PD deficiency variants from Papua New Guinea (PNG) and use the information to examine the extent of molecular heterogeneity underlying G6PD variation in the country. The Wosera G6PD- enzyme was found in a male from the East Sepik Province; it had unique biochemical characteristics compared with other previously described G6PD variants from PNG. The Wosera mutation occurred in exon 12 and led to an Arg463-->His substitution. The Kalo mutation, which led to G6PD deficiency in a male from the Central Province along the south coast of PNG, was found in exon 11 and resulted in an Arg454-->Cys substitution. Although screening for the two molecular mutations using sequence-specific oligonucleotide (SSO) hybridization revealed a wide distribution for the Kalo variant along the coastal belt, no additional copy of the Wosera variant was found in a range of samples. Moreover, 28 G6PD- genes from various parts of PNG failed to hybridize with oligonucleotides encoding either the Kalo or Wosera variants. This suggests that more than the two G6PD mutations exist in PNG, confirming the previously noted biochemical heterogeneity of G6PD deficiency in the Melanesian populations of this region.

Base Sequence↗
PubMed1995

Frequency spectrum of NH bonds in eglin c from spectral density mapping at multiple fields.

The internal mobility of the protein eglin c is characterized with spectral density functions of the NH vectors obtained from heteronuclear NMR relaxation at multiple field strengths (7.04, 11.74, and 14.1 T). The spectral density functions, J(omega), describe the frequency spectrum of the rotational fluctuations of the XH bond vectors (15N-1H and 13C-1H). The spectral density-mapping approach [Peng, J. W., & Wagner, G. (1992a) J. Magn. Reson. 98, 308-332; Peng, J. W., & Wagner, G (1992b) Biochemistry 31, 8571-8586] permits the direct evaluation of J(omega) at the five frequencies 0, omega N, magnitude of omega H - magnitude of omega X, omega H, and magnitude of omega H + magnitude of omega X. The 15N-1H relaxation measurements from three field strengths on 15N-enriched eglin c resulted in 18 relaxation rate constants per NH bond and 13 unique evaluations of each NH spectral density function. Dynamic heterogeneity along the protein backbone is manifested most clearly in spectral density values at lower frequencies (< 100 MHz). The effective value of J(0), J(eff)(0), is the most sensitive probe of dynamics as it is affected by both rapid internal motions and slow chemical exchange processes. Low J(eff)(0) and J(omega N) values are correlated with fast amide proton-deuteron exchange rates; the converse, however, is not observed. Anomalies in J(omega H) and J(magnitude of omega H +/- magnitude of omega N) observed in the first applications of the spectral-mapping approach are now attributable to the high sensitivity of these values to small errors in the rate constants. These anomalies can be reduced by the use of a reduced spectral-mapping procedure. The use of multiple field strengths allows the identification of slow exchange processes manifested as an increase of J(eff)(0) with spectrometer field strength.

Amino Acid Sequence↗
PubMed1995

Solution structure of the pleckstrin homology domain of Drosophila beta-spectrin.

BACKGROUND: The pleckstrin homology (PH) domain, which is approximately 100 amino acids long, has been found in about 70 proteins involved in signal transduction and cytoskeletal function, a frequency comparable to SH2 (src homology 2) and SH3 domains. PH domains have been shown to bind the beta gamma-subunits of G-proteins and phosphatidylinositol 4,5-bisphosphate (PIP2). It is conceivable that the PH domain of beta-spectrin plays a part in the association of spectrin with the plasma membrane of cells. RESULTS: We have solved the solution structure of the 122-residue PH domain of Drosophila beta-spectrin. The overall fold consists of two antiparallel beta-sheets packing against each other at an angle of approximately 60 degrees to form a beta-sandwich, a two-turn alpha-helix unique to spectrin PH domains, and a four-turn C-terminal alpha-helix. One of the major insertions in beta-spectrin PH domains forms a long, basic surface loop and appears to undergo slow conformational exchange in solution. This loop shows big spectral changes upon addition of D-myo-inositol 1,4,5-trisphosphate (IP3). CONCLUSIONS: We propose that the groove at the outer surface of the second beta-sheet is an important site of association with other proteins. This site and the possible lipid-binding site can serve to localize the spectrin network under the plasma membrane. More generally, it has to be considered that the common fold observed for the PH domain structures solved so far does not necessarily mean that all PH domains have similar functions. In fact, the residues constituting potential binding sites for ligands or other proteins are only slightly conserved between different PH domains.

Animals↗