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J Roos

Publications and source records attributed to J Roos.

At least 37 records · Page 2Linked to original sources
PubMed1998

Dap160, a neural-specific Eps15 homology and multiple SH3 domain-containing protein that interacts with Drosophila dynamin.

The discovery of overlapping hot spots of dynamin (Estes, P. S., Roos, J., van der Bliek, A., Kelly, R. B., Krishnan, K. S., and Ramaswami, M. (1996) J. Neurosci. 16, 5443-5456) and the heterotetrameric adaptor 2 complex (Gonzalez-Gaitan, M., and Jäckle, H. (1997) Cell 88, 767-776) in Drosophila nerve terminals led to the concept of zones of active endocytosis close to sites of active exocytosis. The proline-rich domain of Drosophila dynamin was used to identify and purify a third component of the endocytosis zones. Dap160 (dynamin-associated protein 160 kDa) is a membrane-associated, dynamin-binding protein of 160 kDa that has four putative src homology 3 domains and an Eps15 homology domain, motifs frequently found in proteins associated with endocytosis. The binding capacities of the four putative src homology 3 domains were examined individually and in combination and shown to bind known proteins that contained proline-rich domains. Each binding site, however, was different in its preference for binding partners. We suggest that Dap160 is a scaffolding protein that helps anchor proteins required for endocytosis at sites where they are needed in the Drosophila nerve terminal.

Adaptor Protein Complex alpha Subunits↗
PubMed1998

Wide frequency range 31P relaxation in the ion conducting glass LiPO3.

Spin-lattice relaxation studies on the stationary 31P nucleus have been performed in order to investigate to which extent the dynamics of the mobile lithium ions are reflected in the behavior of the glassy network. The temperature dependence of the 31P relaxation, which is governed by the heteronuclear dipole-dipole interaction between lithium and phosphorus, can be described in terms of a Gaussian distribution of activation energies and that over a wide frequency range from about 34 kHz to 81 MHz. A relaxation rate maximum, which provides useful information about correlation times and activation energies of the lithium-ion diffusion process, could only be observed in the rotating frame relaxation measurements.

Lithium↗
PubMed1997

ENP1, an essential gene encoding a nuclear protein that is highly conserved from yeast to humans.

A novel gene in Saccharomyces cerevisiae, ENP1, was found to be essential for growth. The ENP1 gene encodes a protein of 483 amino acids (aa). Nucleotide sequence analysis revealed that the deduced aa sequence of this gene exhibited approx. 60% sequence similarity to the deduced aa sequence of proteins of unknown function in Drosophila, Caenorhabditis elegans and humans. No well defined functional motifs were evident upon analysis of the aa sequence. The protein was found to contain 20% acidic aa residues, with most of them being localized to a very negatively charged domain between aa residues 100 and 150. A construct encoding a fusion protein consisting of the Enp1 protein fused to the c-myc epitope that was either under the control of the ENP1 promoter or the GAL1,10 promoter was prepared. The construct was used to express the protein tagged with the c-myc epitope. Despite the presence of a naturally occurring promoter region with homology to the unfolded protein response element, the level of Enp1mycp remained unchanged after growth of the cells in the presence of tunicamycin, an inhibitor of N-linked glycosylation of proteins. Immunohistochemical studies to define the cellular localization of the Enp1myc protein revealed that it was localized to the nucleus. Accession No.: U50779.

Amino Acid Sequence↗
PubMed1996

Traffic of dynamin within individual Drosophila synaptic boutons relative to compartment-specific markers.

Presynaptic terminals contain several specialized compartments, which have been described by electron microscopy. We show in an identified Drosophila neuromuscular synapse that several of these compartments-synaptic vesicle clusters, presynaptic plasma membrane, presynaptic cytosol, and axonal cytoskeleton-labeled by specific reagents may be resolved from one another by laser scanning confocal microscopy. Using a panel of compartment-specific markers and Drosophila shibire(ts1) mutants to trap an intermediate stage in synaptic vesicle recycling, we have examined the localization and redistribution of dynamin within single synaptic varicosities at the larval neuromuscular junction. Our results suggest that dynamin is not a freely diffusible molecule in resting nerve terminals; rather, it appears localized to synaptic sites by association with yet uncharacterized presynaptic components. In shi(ts1) nerve terminals depleted of synaptic vesicles, dynamin is quantitatively redistributed to the plasma membrane. It is not, however, distributed uniformly over presynaptic plasmalemma; instead, fluorescence images show "hot spots" of dynamin on the plasma membrane of vesicle-depleted nerve terminals. We suggest that these dynamin-rich domains may mark the active zones for synaptic vesicle endocytosis first described at the frog neuromuscular junction.

Animals↗
PubMed1996

Enzymatic formation of dehydrodolichal and dolichal, new products related to yeast dolichol biosynthesis.

Two new polyprenyl products in addition to dehydrodolichol and dolichol were detected by two-plate silica gel thin layer chromatography of nonpolar products formed from [1-14C]isopentenyl diphosphate and farnesyl diphosphate in the reaction with a crude 1,000 x g supernatant of yeast homogenates in the presence of NADPH. The new products were indistinguishable from authentic dehydrodolichal and dolichal. Analyses of the time-dependent and pH-dependent formation of the four products including dehydrodolichal and dolichal suggested that the biosynthetic pathway from dehydrodolichol leading to dolichal is different from that to dolichol. In double-labeled experiments with a combination of -l-14C-isopentenyl diphosphate and a [4B-3H]NADPH-generating system, the ratio of 3H- and 14C-derived radioactivities found in dolichal was six times higher than that in dolichol. A small amount of 3H-labeled dehydrodolichol was also detected. Considering the fact that dolichol is synthesized from dehydrodolichol (Sagami, H., Kurisaki, A., and Ogura, K. (1993) J. Biol. Chem. 268, 10109-10113), we propose that dehydrodolichol is a common branch point intermediate in the biosynthetic pathways leading to dolichal and dolichol and that dehydrodolichal is an intermediate in the pathway from dehydrodolichol to dolichal.

Carbon Radioisotopes↗
PubMed1996

The OST4 gene of Saccharomyces cerevisiae encodes an unusually small protein required for normal levels of oligosaccharyltransferase activity.

Sodium vanadate is an effective drug for the enrichment of yeast mutants defective in glycosylation reactions that are carried out in the Golgi complex. We have isolated vanadate-resistant, hygromycin B-sensitive mutants that act at very early steps of N-linked glycosylation, occurring in the endoplasmic reticulum. Here we describe the phenotypic characterization of ost4, a vanadate-resistant mutant that is defective in oligosaccharyltransferase (OTase) activity both in vivo and in vitro. The OST4 open reading frame is unusual in that it predicts a protein of only 36 amino acids. We demonstrate that the OST4 gene product is, in fact, an unusually small protein of approximately 3.6 kDa, predicted to lie almost entirely in the hydrophobic environment of the membrane. Strains carrying a disruption of the OST4 gene are viable but grow poorly at 25 degrees C. The null mutant is inviable at 37 degrees C, demonstrating that the OST4 gene product is essential for growth at high temperatures. Deletion of the OST4 gene greatly diminishes OTase activity but does not abolish it. These results suggest that the OST4 gene encodes a subunit or accessory component of OTase that is essential at high temperature.

Algorithms↗
PubMed1996

Over-expression of S. cerevisiae G1 cyclins restores the viability of alg1 N-glycosylation mutants.

In budding yeast, one of three G1 cyclins is required for progression though START, when cells commit to a further round of cell division. We have identified mutations in ALG1 (ERC14), a gene required for N-glycosylation, which are inviable in a cln1 cln2 background but are rescued by over-expression of CLNs. CLN1 and CLN2 are much more efficient than CLN3 in rescuing the erc14-1 allele. The erc14-1 allele results in a significant N-glycosylation defect, and no rescue of this defect by CLN1 over-expression was detected. These data suggest that CLN over-expression could be allowing cells to live with lower levels of N-glycosylation, possibly by overcoming a checkpoint sensitive to N-glycosylation capacity. A plasmid suppressor of alg1, PSA1, encodes a 361 amino-acid protein with homology to NDP-hexose pyrophosphorylases, the enzymes that catalyze the formation of activated sugar nucleotides. PSA1 is an essential gene, and PSA1 transcription is nearly co-ordinately regulated with CLN2 transcription, peaking near START. Co-ordinate regulation of glycosylation, sugar nucleotide metabolism, and cell-cycle progression through G1 may be a feature that ensures adequate cell-wall precursors are present before bud emergence.

Alleles↗
PubMed1995

Evaluation of bone density using cutting resistance measurements and microradiography: an in vitro study in pig ribs.

A method using cutting resistance measurements during low-speed threading for identification of various bone densities has been evaluated with regard to its precision and potential. Pig ribs were used as test samples. Differing hand pressure, minor deviation (5 degrees) from a vertical tapping direction and individual threading did not reveal any significant differences in cutting resistance values. After implants were inserted into the threaded canals, the total bone as well as trabecular and compact bone areas surrounding the implants were calculated via a computer program and using microradiographs of the bone test samples. The outcome of the cutting resistance measurements was compared with that of the microradiographic technique, and good agreement was observed between the two procedures in the ability to identify bone density. Therefore, cutting resistance measurements may in the future also be used to clinically identify bone qualities in jaws.

Animals↗
PubMed1995

Identification of bone quality in conjunction with insertion of titanium implants. A pilot study in jaw autopsy specimens.

Ten autopsy jaw specimens (6 mandibles, 4 maxillae) were used for cutting resistance measurements during low-speed threading. Overall, 31 sites were analyzed where implants were inserted into threaded canals. Bone area measurements were performed around the implants as described previously. The cutting resistance values together with the total bone area values were found to be higher in mandibles than in maxillae, and a tendency towards higher values was seen in incisor regions compared with premolar regions. Furthermore, an intraindividual comparison between the true cutting resistance and the bone density values of prepared sites showed a statistically significant correlation. The method with cutting resistance measurements for evaluation of bone quality seems therefore to be reliable, at least when used in human autopsy jaw bone specimens.

Aged↗
PubMed1995

[Evaluation and analysis of social relationships of children in clinical practice and research: "Social Relationship Scale for Children"].

The Social Relationship Procedure for Children (Soziales Beziehungsverfahren f¿ur Kinder, SOBEKI), a technique employing figure tasks and interviewing, is a new clinical psychology assessment instrument for use with children. With this instrument it is possible to (a) determine the significant others (social network) of 6- to 12-year-old children, (b) measure how specific functions are divided among members of a child's social networks, and (c) visualizing cohesion and hierarchical structures of the children's networks within and outside their families. In the present paper the theoretical foundations, administration and assessment of the procedure are outlined. In addition, the results of a comparison of children with psychiatric disorders and a healthy control group are presented.

Child↗