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H A Meyer

Publications and source records attributed to H A Meyer.

At least 19 recordsLinked to original sources
PubMed2000

Interactions between Spc2p and other components of the endoplasmic reticulum translocation sites of the yeast Saccharomyces cerevisiae.

In yeast, the endoplasmic reticulum membrane proteins Sec11p and Spc3p are essential for the cleavage of signal peptides of nascent polypeptide chains during their passage through translocation sites. Genetic and biochemical experiments demonstrate that Sec11p and Spc3p are tightly associated with two other proteins, Spc1p and Spc2p, whose functions are largely unknown. Using anti-Spc2p antibodies, we show here that this heterotetrameric complex associates with Sbh1p and Sbh2p, the beta-subunits of the Sec61p complex and the Ssh1p complex, respectively. Depletion of Spc2p decreased the enzymatic activity of the SPC in vitro, led to a loss of Spc1p, and led to a down-regulation of the amount of Sec11p and Spc3p in the endoplasmic reticulum. Moreover, the deletion of Spc2p also decreased the expression level of Sbh2p. These data implicate that Spc2p not only enhances the enzymatic activity of the SPC but also facilitates the interactions between different components of the translocation site.

Base Sequence↗
PubMed2000

Mammalian Sec61 is associated with Sec62 and Sec63.

In yeast, efficient protein transport across the endoplasmic reticulum (ER) membrane may occur co-translationally or post-translationally. The latter process is mediated by a membrane protein complex that consists of the Sec61p complex and the Sec62p-Sec63p subcomplex. In contrast, in mammalian cells protein translocation is almost exclusively co-translational. This transport depends on the Sec61 complex, which is homologous to the yeast Sec61p complex and has been identified in mammals as a ribosome-bound pore-forming membrane protein complex. We report here the existence of ribosome-free mammalian Sec61 complexes that associate with two ubiquitous proteins of the ER membrane. According to primary sequence analysis both proteins display homology to the yeast proteins Sec62p and Sec63p and are therefore named Sec62 and Sec63, respectively. The probable function of the mammalian Sec61-Sec62-Sec63 complex is discussed with respect to its abundance in ER membranes, which, in contrast to yeast ER membranes, apparently lack efficient post-translational translocation activity.

Amino Acid Sequence↗
PubMed1998

Mood influences on automatic and controlled semantic priming.

Mood effects on automatic and controlled components of semantic priming were examined. After a neutral or positive mood manipulation, subjects underwent two blocks of a priming task. Automatic and strategic priming processes were operationally differentiated by the assumption that automatic priming remains constant during the task, whereas controlled priming develops slowly during the course of the experiment. In the first block the priming effect was greater for happy than for neutral mood participants. In the second block the priming effect was greater for neutral mood than for happy participants. The results confirm the hypothesis of a mood-dependent processing change: During early trials priming is based on automatic processing facilitated by positive mood. This processing mode is later superseded by controlled processes aided by neutral mood.

Adult↗
PubMed1997

The yeast SPC22/23 homolog Spc3p is essential for signal peptidase activity.

In eucaryotic cells signal sequences of secretory and membrane proteins are cleaved by the signal peptidase complex during their transport into the lumen of the endoplasmic reticulum. The signal peptidase complex in yeast consists of four subunits. To date, three of these subunits have been functionally characterized. One of them, the Sec11p, is essential for viability of yeast cells. It shows significant homology to the mammalian SPC18 and SPC21 as well as to bacterial leader peptidases. Two other subunits, Spc1p and Spc2p, have been shown to be homologous to mammalian SPC12 and SPC25, respectively, and are not essential for protein translocation or signal peptide cleavage. We have purified and analyzed the fourth subunit of yeast signal peptidase, Spc3p. The protein is essential for viability of yeast cells. Depletion of SPC3 leads to accumulation of precursors of secretory proteins in vivo and to the loss of the signal peptidase activity in vitro. Therefore, in contrast to the bacterial leader peptidases, yeast signal peptidase requires a second subunit for its function.

Amino Acid Sequence↗
PubMed1996

Structurally related Spc1p and Spc2p of yeast signal peptidase complex are functionally distinct.

Two subunits of the mammalian signal peptidase complex, SPC12 and SPC25, share similar membrane topologies with the majority of each protein oriented toward the cytoplasm. Such similarities may suggest that these proteins perform redundant functions in signal peptidase activity. In the present study, we addressed this issue through analysis of the yeast homologs to SPC12 and SPC25, Spc1p and Spc2p. We show that both Spc1p and Spc2p are nonessential for signal peptidase activity and growth of yeast cells and that null mutations in the genes encoding Spc1p and Spc2p are synthetically lethal with a conditional mutation affecting Sec11p, an essential subunit of yeast signal peptidase. However, a high copy plasmid encoding Spc1p suppresses the conditional sec11 mutation, whereas the corresponding plasmid encoding Spc2p does not suppress sec11. Moreover, Spc2p, but not Spc1p, is important for signal peptidase activity and cell viability at high temperatures. These results indicate that although both Spc1p and Spc2p are noncatalytic, they are functionally distinct. Evidence is also presented that a double mutant lacking Spc1p and Spc2p grows well relative to wild type yeast cells, indicating that the signal peptidase complex missing at least two of its subunits is sufficient for signal peptidase activity in vivo.

Amino Acid Sequence↗
PubMed1996

Effects of antisense DNA against the alpha-sarcin stem-loop structure of the ribosomal 23S rRNA.

Antisense DNAs complementary against various sequences of the alpha-sarcin domain (C2646-G2674) of 23S rRNA from Escherichia coli were hybridized to naked 23S rRNA as well as to 70S ribosomes. Saturation levels of up to 0.4 per 70S ribosome were found, the identical fraction was susceptible to the attack of the RNase alpha-sarcin. The hybridization was specific as demonstrated with RNase H digestion, sequencing the resulting fragments and blockage of the action of alpha-sarcin. The RNase alpha-sarcin seems to approach its cleavage site from the 3' half of the loop of the alpha-sarcin domain. Hybridization is efficiently achieved at 37 degrees C and can extend at least into the 3' strand of the stem of the alpha-sarcin domain. However, the inhibition of alpha-sarcin activity is observed at 30 degrees C but not at 37 degrees C. For a significant inhibition of poly(Phe) synthesis the temperature had to be lowered to 25 degrees C. The results imply that the alpha-sarcin domain changes its conformation during protein synthesis and that the conformational changes may include a melting of the stem of the alpha-sarcin domain.

Base Sequence↗
PubMed1994

[Reducing ambiguity: semantic statistical studies of "normal" probands, neurotic patients, borderline patients and schizophrenic patients].

The present study tries to answer three questions: 1.) Do patients with neurotic disorders differ from normals by a stronger tendency to avoid or reduce ambiguity? 2.) Does the tendency to avoid or reduce ambiguity increase with increasing ambiguity of the stimulus? 3.) Does the avoidance or reduction of ambiguity increase with affects of anxiety and hostility? In order to answer these questions, Ertel's dogmatism-dictionary was applied to the answers of 30 normals, 30 patients with neurotic disorders, 30 borderline-patients, 25 acute and 25 chronic schizophrenics in the Holtzman Inkblot Technique (HIT). According to the results, (1) patients with neurotic disorders do not differ from normals by a stronger tendency to avoid or reduce ambiguity. 2.) The tendency to avoid or reduce ambiguity increases with measures of increasing stimulus ambiguity of the HIT cards in all diagnostic groups studied with the exception of chronic schizophrenics. As far as response ambiguity (variability of interpretation) is concerned, only in chronic schizophrenics the tendency to avoid or reduce ambiguity decreases with increasing response ambiguity. 3.) The avoidance or reduction of ambiguity increases with affects of anxiety and/or aggression assessed by HIT-measures in all diagnostic groups studied with the exception of normals and chronic schizophrenics. In both normals and chronic schizophrenics, the reduction of ambiguity decreases significantly with increasing anxiety, in chronic schizophrenics the reduction of ambiguity decreases significantly with an increase of low levels of aggression.

Adult↗
PubMed1992

[Cognitive style of schizophrenic patients: ambiguity avoidance and decreased abstract thinking].

The hypothesis of specific cognitive dynamics in schizophrenics is derived and tested in this study. This cognitive style should be characterized by a reduction of cognitive ambiguity and could be demonstrated in borderline patients in a previous study. This hypothesis is tested by applying Ertel's (1972) DOTA-dictionary to responses of 25 acute and 25 chronic schizophrenics in the Holtzman Inkblot Technique. Furthermore the level of abstractness of the responses is investigated with the method of Günther and Groeben (1978). According to the results both groups of schizophrenics had a significantly higher "Dogmatismus-Quotient" (Ertel, 1972) than a sample of neurotics, but did not differ from borderline patients. Both acute and chronic schizophrenics used significantly less abstract nouns than borderline patients and neurotics. In contrast to borderline patients the reduction of cognitive ambiguity in schizophrenics is not connected with strong affects of anxiety and hostility.

Adult↗
PubMed1975

[Hepatic amebiasis in the Kilimanjaro region. Serodiagnosis on micro-specimens of dried blood and attempts at treatment with tinidazole (fasigyn)].

Amoebic dysentery appears to be rare in the northeast of Tanzania. Hepatic amoebiasis, on the other hand, is apparently widespread since at least 200 cases are seen every year at the Kilimanjaro Christian Medical Centre. This incidence of cases enabled us to carry out trials on the spot with a new imidazole derivative, Tinidazole. Formerly the difficult diagnosis based on clinical symptoms had to be buttressed by radiological evidence and possibly by the result of puncture. Indirect fluorescent antibody tests for the diagnosis of amoebiasis were performed elsewhere on all the patients, using for this purpose microspecimens of dried blood. In 12 cases out of 34 an agglutination test with sensitized latex particles was performed on the spot. This latter test has the practical advantage of being easy to employ. It cannot, however, be considered as a screening test since it is subject to downward and upward errors. The indirect fluorescent antibody test has been found to be constantly and highly positive, certain antibody titres attaining 1/6400. This fully confirms the value of the method even under special working conditions. Seventeen of our 34 patients (2 women and 15 men ranging in age from 20 to 75 years) were treated with 2 g of Tinidazole per day in a single dose for 2 to 3 consecutive days. Puncture to evacuate pus was also performed where abscesses had collected. Tolerance on the whole was good without a single sign of cardiovascular or urinary toxicity. However, paraesthesia of the hands was observed in one case, transitory thrombocytopenia in one other patient, and increased alkaline phosphatases. Minor disorders were also observed in our series of patients: mild vertigo (7 cases), headache (6 cases), and dry mouth (2 cases). After 8 months the therapeutic results were as follows: 12 complete cures out of 17, 2 improvements with final cure probable, 3 partial failures necessitating supplementary treatment with Metronidazole (2.4 g per day for 2 days). These preliminary trials appear to the encouraging and the study is being continued with series compared with cases treated with Emetine or Metronidazole.

Adult↗