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M G Waters

Publications and source records attributed to M G Waters.

At least 37 records · Page 2Linked to original sources
PubMed1997

Adherence of Candida albicans to experimental denture soft lining materials.

STATEMENT OF PROBLEM: Colonization of denture soft lining materials by Candida albicans can result in clinical problems. Two experimental silicone soft lining materials have been developed and demonstrate good physical properties. PURPOSE OF STUDY: The aim of this study was to determine the extent of candidal adherence to these materials compared with a commercially available soft lining material and an acrylic resin denture base. MATERIAL AND METHODS: The experimental materials were constructed in a stainless-steel mold, and their surface energies were determined with a dynamic contact angle analyzer. The adherence of three strains of C. albicans was determined with an in vitro assay. In addition, one test strain was used to determine the effect on adherence of precoating the materials with whole saliva. RESULTS: Adhesion to all materials was strain variable, with the lowest adherence recorded for the two experimental materials. Decreased adherence was also apparent after precoating the materials with saliva. Correlation between surface energy of the material and the degree of candidal adhesion was seen for one strain, but no correlation was seen for the other two strains. CONCLUSION: Adherence of C. albicans to the two experimental silicone soft lining materials was significantly less than that for an acrylic resin denture base and a commercially available soft lining material.

Acrylic Resins↗
PubMed1997

Characterization of a novel yeast SNARE protein implicated in Golgi retrograde traffic.

The protein trafficking machinery of eukaryotic cells is employed for protein secretion and for the localization of resident proteins of the exocytic and endocytic pathways. Protein transit between organelles is mediated by transport vesicles that bear integral membrane proteins (v-SNAREs) which selectively interact with similar proteins on the target membrane (t-SNAREs), resulting in a docked vesicle. A novel Saccharomyces cerevisiae SNARE protein, which has been termed Vti1p, was identified by its sequence similarity to known SNAREs. Vti1p is a predominantly Golgi-localized 25-kDa type II integral membrane protein that is essential for yeast viability. Vti1p can bind Sec17p (yeast SNAP) and enter into a Sec18p (NSF)-sensitive complex with the cis-Golgi t-SNARE Sed5p. This Sed5p/Vti1p complex is distinct from the previously described Sed5p/Sec22p anterograde vesicle docking complex. Depletion of Vti1p in vivo causes a defect in the transport of the vacuolar protein carboxypeptidase Y through the Golgi. Temperature-sensitive mutants of Vti1p show a similar carboxypeptidase Y trafficking defect, but the secretion of invertase and gp400/hsp150 is not significantly affected. The temperature-sensitive vti1 growth defect can be rescued by the overexpression of the v-SNARE, Ykt6p, which physically interacts with Vti1p. We propose that Vti1p, along with Ykt6p and perhaps Sft1p, acts as a retrograde v-SNARE capable of interacting with the cis-Golgi t-SNARE Sed5p.

Adenosine Triphosphatases↗
PubMed1996

Cyclical deformation behaviour of denture soft lining materials.

OBJECTIVES: The purpose of the study was to examine and describe the deformation behaviour of five denture soft lining materials under dynamic cyclic loading over a range of applied forces using apparatus designed to simulate masticatory performance. METHODS: Five lining materials were tested over 5-min periods using an Instron tensile testing machine that was modified to measure load and strain semi-continuously during cyclic loading. RESULTS: Strain energy and strain energy densities and moduli values for each material were calculated. The strain energy absorbed at separate times during the cycling period demonstrated the elastic behaviour of the materials over the 5-min simulated chewing cycle. CONCLUSIONS: All materials demonstrated elastic but not perfectly linearly elastic behaviour over the chosen loading and cycling frequency. Molloplast B absorbed most energy at the lower testing loads and Novus absorbed most energy at the higher loads.

Acrylic Resins↗
PubMed1996

Effect of surface modified fillers on the water absorption of a (RTV) silicone denture soft lining material.

OBJECTIVES: The purpose of the present study was to modify the filler content of an experimental room-temperature vulcanizing (RTV) lining material that demonstrated high water sorption in order to produce a material with low sorption properties. METHODS: Three new formulations were prepared, each containing different hydrophobic silane-treated silica fillers. Water sorption properties for specimens obtained from these formulations were determined using standard experimental techniques. RESULTS: All formulations demonstrated greatly reduced water absorption and low volume change. CONCLUSIONS: An experimental RTV poly(dimethylsiloxane) denture soft lining material having low water sorption properties has been produced.

Absorption↗
PubMed1996

Assembly of the ER to Golgi SNARE complex requires Uso1p.

Uso1p, a Saccharomyces cerevisiae protein required for ER to Golgi transport, is homologous to the mammalian intra-Golgi transport factor p115. We have used genetic and biochemical approaches to examine the function of Uso1p. The temperature-sensitive phenotype of the uso1-1 mutant can be suppressed by overexpression of each of the known ER to Golgi v-SNAREs (Bet1p, Bos1p, Sec22p, and Ykt6p). Overexpression of two of them, BET1p and Sec22p, can also suppress the lethality of delta uso1, indicating that the SNAREs function downstream of Uso1p. In addition, overexpression of the small GTP-binding protein Ypt1p, or of a gain if function mutant (SLY1-20) of the t-SNARE associated protein Sly1p, also confers temperature resistance. Uso1p and Ypt1p appear to function in the same process because they have a similar set of genetic interactions with the v-SNARE genes, they exhibit a synthetic lethal interaction, and they are able to suppress temperature sensitive mutants of one another when overexpressed. Uso1p acts upstream of, or in conjunction with, Ypt1p because overexpression of Ypt1p allows a delta uso1 strain to grow, whereas overexpression of Uso1p does not suppress a delta ypt1 strain. Finally, biochemical analysis indicates that Uso1p, like Ypt1p, is required for assembly of the v-SNARE/t-SNARE complex. The implications of these findings, with respect to the mechanism of vesicle docking, are discussed.

Base Sequence↗
PubMed1996

Localization of a yeast early Golgi mannosyltransferase, Och1p, involves retrograde transport.

To analyze the mechanism of integral membrane protein localization in the early Golgi apparatus of Saccharomyces cerevisiae, we have used Och1p, a cis-Golgi mannosyltransferase. A series of influenza virus hemagglutinin (HA) epitope-tagged fusion proteins was constructed in which invertase is appended to the Golgi-luminal carboxy terminus of full-length Och1p. Several constructs included a Kex2p cleavage site between the Och1p and invertase moieties to monitor transit to the Kex2p-containing TGN. Cells expressing an Och1p-invertase fusion do not secrete invertase, but those expressing an Och1p-Kex2p site-invertase fusion protein secrete high levels of invertase in a Kex2p-dependent manner. The Och1p-Kex2p site-invertase fusion protein is cleaved with a half-time of 5 min, and the process proceeds to completion. Before cleavage the protein receives glycosyl modifications indicative of passage through the medial- and trans-Golgi, therefore cleavage occurs after ordered anterograde transport through the Golgi to the TGN. Transit to distal compartments is not induced by the invertase moiety, since noninvertase fusion constructs encounter the same glycosyltransferases and Kex2p as well. The Och1p-HA moiety, irrespective of whether it is generated by cleavage of the fusion protein in the TGN or synthesized de novo, is degraded with a half-time of about 60 min. Thus, the half-time of degradation is 12-fold longer than the time required to reach the TGN. At steady state, de novo-synthesized and TGN-generated HA epitope-tagged Och1p reside in a compartment with a buoyant density identical to that of wild-type Och1p and distinct from that of the vacuole or the TGN. Finally, och1 null cells that express an Ochlp fusion construct known to rapidly encounter the TGN glycosylate invertase to the same extent as wild-type cells, indicating that they have phenotypically wild-type Och1p activity. These results lead us to propose a model for Och1p-HA localization that involves movement to distal compartments, at least as far as the TGN, followed by retrieval to the cis compartment, presumably by vesicular transport.

Amino Acid Sequence↗
PubMed1996

Evidence that phospholipase D mediates ADP ribosylation factor-dependent formation of Golgi coated vesicles.

Formation of coatomer-coated vesicles from Golgi-enriched membranes requires the activation of a small GTP-binding protein, ADP ribosylation factor (ARF). ARF is also an efficacious activator of phospholipase D (PLD), an activity that is relatively abundant on Golgi-enriched membranes. It has been proposed that ARF, which is recruited onto membranes from cytosolic pools, acts directly to promote coatomer binding and is in a 3:1 stoichiometry with coatomer on coated vesicles. We present evidence that cytosolic ARF is not necessary for initiating coat assembly on Golgi membranes from cell lines with high constitutive PLD activity. Conditions are also described under which ARF is at most a minor component relative to coatomer in coated vesicles from all cell lines tested, including Chinese hamster ovary cells. Formation of coated vesicles was sensitive to ethanol at concentrations that inhibit the production of phosphatidic acid (PA) by PLD. When PA was produced in Golgi membranes by an exogenous bacterial PLD, rather than with ARF and endogenous PLD, coatomer bound to Golgi membranes. Purified coatomer also bound selectively to artificial lipid vesicles that contained PA and phosphatidylinositol (4,5)-bisphosphate (PIP2). We propose that activation of PLD and the subsequent production of PA are key early events for the formation of coatomer-coated vesicles.

ADP-Ribosylation Factors↗
PubMed1995

p115 is a general vesicular transport factor related to the yeast endoplasmic reticulum to Golgi transport factor Uso1p.

A recently discovered vesicular transport factor, termed p115, is required along with N-ethylmaleimide-sensitive fusion protein (NSF) and soluble NSF attachment proteins for in vitro Golgi transport. p115 is a peripheral membrane protein found predominantly on the Golgi. Biochemical and electron microscopic analyses indicate that p115 is an elongated homodimer with two globular "heads" and an extended "tail" reminiscent of myosin II. We have cloned and sequenced cDNAs for bovine and rat p115. The predicted translation products are 90% identical, and each can be divided into three domains. The predicted 108-kDa bovine protein consists of an N-terminal 73-kDa globular domain followed by a 29-kDa coiled-coil dimerization domain, a linker segment of 4 kDa, and a highly acidic domain of 3 kDa. p115 is related to Uso1p, a protein required for endoplasmic reticulum to Golgi vesicular transport in Saccharomyces cerevisiae, which has a similar "head-coil-acid" domain structure. The p115 and Uso1p heads are similar in size, have approximately 25% sequence identity, and possess two highly homologous regions (62% and 60% identity over 34 and 53 residues, respectively). There is a third region of homology (50% identity over 28 residues) between the coiled-coil and acidic domains. Although the acidic nature of the p115 and Uso1p C termini is conserved, the primary sequence is not. We discuss these results in light of the proposed function of p115 in membrane targeting and/or fusion.

Amino Acid Sequence↗
PubMed1995

Wettability of denture soft-lining materials.

Data on the wettability of long-term resilient denture base lining materials have previously been obtained by static methods. This study determined the dynamic contact angle of a range of long-term resilient lining materials and the surface free energy properties of these materials. This method was a rapid and convenient method for determining wettability parameters. The equilibrium contact angle revealed the Flexor and Novus materials to be the least wetted with the Molloplast-B material, and CoeSuper-Soft material was wetted similarly to Trevalon material. The contact angle hysteresis indicated that all the soft-lining materials tested would improve denture stability under dislodgment forces. The surface-free energies appeared to be similar for all the soft-lining materials but were significantly lower than that of Trevalon.

Acrylic Resins↗
PubMed1992

A novel 115-kD peripheral membrane protein is required for intercisternal transport in the Golgi stack.

We have used an in vitro Golgi protein transport assay dependent on high molecular weight (greater than 100 kD) cytosolic and/or peripheral membrane proteins to study the requirements for transport from the cis- to the medial-compartment. Fractionation of this system indicates that, besides the NEM-sensitive fusion protein (NSF) and the soluble NSF attachment protein (SNAP), at least three high molecular weight protein fractions from bovine liver cytosol are required. The activity from one of these fractions was purified using an assay that included the second and third fractions in a crude state. The result is a protein of 115-kD subunit molecular mass, which we term p115. Immunodepletion of the 115-kD protein from a purified preparation with mAbs removes activity. Peptide sequence analysis of tryptic peptides indicates that p115 is a "novel" protein that has not been described previously. Gel filtration and sedimentation analysis indicate that, in its native state, p115 is a nonglobular homo-oligomer. p115 is present on purified Golgi membranes and can be extracted with high salt concentration or alkaline pH, indicating that it is peripherally associated with the membrane. Indirect immunofluorescence indicates that p115 is associated with the Golgi apparatus in situ.

Animals↗
PubMed1991

'Coatomer': a cytosolic protein complex containing subunits of non-clathrin-coated Golgi transport vesicles.

Golgi-derived coated vesicles contain a set of coat proteins of relative molecular mass 160,000 (Mr 160K; alpha-COP), 110K (beta-COP), 98K (gamma-COP) and 61K (delta-COP), and several smaller subunits. We have now identified and purified a cytosolic complex containing the same four coat proteins as those of Golgi transport vesicles. We term this complex the Golgi coat promoter or 'coatomer'. The coatomer also contains polypeptides of Mr 36K, 35K and 20K. It represents about 0.2% of soluble cytosolic protein. Gel filtration of unfractionated cytosol indicates that beta-COP resides exclusively in the coatomer complex. The complex seems to be a likely candidate for the unassembled precursor of Golgi coated vesicles, and its purification should help investigations of the role of coat proteins in membrane budding, for which it is necessary to use a refined cell-free system.

Adaptor Protein Complex beta Subunits↗
PubMed1991

Proteins involved in vesicular transport and membrane fusion.

In the past year, new information about proteins involved in vesicular transport has been plentiful. Particularly noteworthy are the complementary findings that Sec17p is required for vesicle consumption in endoplasmic reticulum-to-Golgi transport in yeast and that an analogous activity in mammalian cells, termed SNAP, is required for transport from the cis to the medial cisternae of the Golgi apparatus.

Animals↗
PubMed1988

Prepro-alpha-factor has a cleavable signal sequence.

MAT alpha Saccharomyces cerevisiae secrete a small peptide mating pheromone termed alpha-factor. Its precursor, prepro-alpha-factor, is translocated into the endoplasmic reticulum and glycosylated at three sites. The glycosylated form is the major product in a yeast in vitro translation/translocation system. However, there is another translocated, nonglycosylated product that contains a previously unidentified modification. Contrary to previous results suggesting that the signal sequence of prepro-alpha-factor is not cleaved, amino-terminal radiosequencing has identified this product as prepro-alpha-factor without its signal sequence, that is, pro-alpha-factor. The translocated, glycosylated proteins are also processed by signal peptidase. Moreover, we have found that both purified eukaryotic and prokaryotic signal peptidase can process prepro-alpha-factor. Experiments using a yeast secretory mutant (sec 18) blocked in transport from the endoplasmic reticulum to the Golgi indicate that the protein is also cleaved in vivo. Finally, characterization of the Asn-linked oligosaccharide present on pro-alpha-factor in the yeast in vitro system by use of specific glucosidase and mannosidase inhibitors indicates that they have had the three terminal glucoses and probably one mannose removed. Therefore they most likely consist of Man8GlcNAc2 structures, identical to those found in the endoplasmic reticulum in vivo.

Amino Acid Sequence↗
PubMed1988

70K heat shock related proteins stimulate protein translocation into microsomes.

A yeast cytosol is shown to contain two distinct activities that stimulate protein translocation across microsomal membranes. One activity was purified. It consists of two constitutively expressed 70K heat shock related proteins that increase the rate of translocation. Possible mechanisms of action of these proteins are discussed.

Adenosine Triphosphate↗
PubMed1986

Localization of L-lactate dehydrogenase in mitochondria.

Relatively small but persistent amounts of L-lactate dehydrogenase (LDH) activity were found in mitochondrial preparations isolated from liver of the rat. Using a variety of cytosolic markers, it was found that essentially no cytosolic contamination was present. Respiratory velocities and respiratory control with L-lactate were somewhat lower than with glutamate, but equal or superior to those with pyruvate. Agarose gel electrophoresis showed LDH isoenzymes in mitochondria similar to that in corresponding cytosol. Subtilisin BPN', a bacterial protease, was incubated with intact mitochondria and enzyme activities were measured. Following mitochondrial disruption, the proteolytic treatment was repeated. Digitonin was also used in the fractionation of mitochondria. These techniques helped to determine the location of the LDH in the mitochondria as being mainly in the outer membrane and periplasmic space.

Animals↗
PubMed1986

Secretory protein translocation in a yeast cell-free system can occur posttranslationally and requires ATP hydrolysis.

We describe an in vitro system with all components derived from the yeast Saccharomyces cerevisiae that can translocate a yeast secretory protein across microsomal membranes. In vitro transcribed prepro-alpha-factor mRNA served to program a membrane-depleted yeast translation system. Translocation and core glycosylation of prepro-alpha-factor were observed when yeast microsomal membranes were added during or after translation. A membrane potential is not required for translocation. However, ATP is required for translocation and nonhydrolyzable analogues of ATP cannot serve as a substitute. These findings suggest that ATP hydrolysis may supply the energy required for translocation of proteins across the endoplasmic reticulum.

Adenosine Triphosphate↗
PubMed1986

Protein translocation across the yeast microsomal membrane is stimulated by a soluble factor.

We have found that a soluble activity present in the postribosomal supernatant fraction of Saccharomyces cerevisiae stimulates posttranslational translocation of yeast prepro-alpha-factor across yeast microsomal membranes. Stimulation of translocation is not due to a nonspecific affect on ATP levels. The activity is likely to be due to protein(s) as it is destroyed by N-ethylmaleimide, protease, or heat treatment but not by incubation with RNase. Its apparent sedimentation coefficient is approximately 9.6 S.

Biological Transport, Active↗