Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proteolytic enzyme, thermolysin, degraded the external segment of the membrane glycoprotein of intact vesicular stomatitis (VS) virions but left behind a small nonglycosylated fragment, presumably embedded in the virion membrane. Other proteases generated membrane-associated glycoprotein fragments differing somewhat in molecular weight. The thermolysin-resistant, virion-associated fragment, which can be selectively solubilized by either Triton X-100 or chloroform/methanol, has a molecular weight of 5,200. Amino acid analysis of the glycoprotein fragment reveals a preponderance of hydrophobic amino acids (64% of the residues); the amino-terminal amino acid is alanine as determined by dansylation. Cyanogen bromide digestion of the tail fragment generated two peptides, confirming the presence of one methionine residue per thermolysin-resistant glycoprotein fragment. The secondary structure of this glycoprotein tail peptide is maintained by at least one disulfide bridge. Thermolysin treatment is isolated VS viral glycoprotein in the presence of Triton X-100 also generated a hydrophobic peptide fragment which is very similar to the virion-associated glycoprotein fragment. The amino acid terminus of intact glycoprotein was also found to be alanine as was its dansylated Triton-micellar fragment that resisted thermolytic degradation; this finding suggests that the amino-terminal end of the VS viral glycoprotein is embedded in the virion membrane. These results suggest that the VS viral glycoprotein is an amphipathic molecule, the hydrophilic portion of which contains all the carbohydrate and a lipophilic tail segment which forms lipid or detergent micelles, thus rendering it resistant to proteolysis.
 ...
PMID:Association of vesicular stomatitis virus glycoprotein with virion membrane: characterization of the lipophilic tail fragment. 16

The proton decoupled 40.48 M Hz 31P NMR spectrum of intact and unperturbed membrane-enclosed vesicular stomatitis virus (sterotype Indiana) exhibited two distinct maxima. These can be resolved into a narrow, symmetric line and a broad asymmetric line. The 31P NMR spectrum of a multilamellar (unsonicated) preparation of the extracted viral lipids exhibited a line shape similar to that of the intact virus. A sonicated vesicle preparation of the extracted viral lipids exhibited a narrow symmetric line. The narrow component in the intact virus spectrum may be attributed to small membrane fragments. Phospholipase C digestion of the intact virus resulted in substantial reduction in intensity of both components which suggests that much of the contribution to both peaks is due to phosphate in the phospholipid polar head groups. The phospholipid phosphates in both sonicated and unsonicated preparations of the extracted viral lipids exhibited substantially longer relaxation times than did those in the intact virus. The short relaxation time emanating from the intact virus preparation is caused by immobilization of the phospholipid head groups which could be due to lipid-protein interactions. Trypsin treatment of vesicular stomatitis virions, which results in complete removal of the exterior hydrophilic segment of the membrane glycoprotein, increased the 31P relaxation time to a value similar to that observed in the protein-free total lipid extracts; this finding provides supporting evidence for the role of virus glycoprotein in shortened relaxation times. A reversible temperature-dependent change in apparent line width and absence of an effect of cholesterol on the 31P phospholipid spectrum were also demonstrated.
 ...
PMID:The structure of vesicular stomatitis virus membrane. A phosphorus nuclear magnetic resonance approach. 18 70

Membrane assembly was observed to proceed in cell-free extracts. Specifically, the membrane glycoprotein of vesicular stomatitis virus was synthesized in crude extracts of wheat germ in the presence of membrane vesicles derived from pancreatic endoplasmic reticulum. The resulting glycoprotein spans the lipid bilayer asymmetrically, is glycosylated, and is indistinguishable in these respects from the form of the glycoprotein found in the rough endoplasmic reticulum of virus-infected cells. Both glycosylation and asymmetric transmembrane insertion of the glycoprotein into membranes in vitro require protein synthesis in the presence of membranes. The carboxyl-terminal 5% of the polypeptide chain is located on the external surface of vesicles, corresponding to the cytoplasmic surface of the endoplasmic reticulum in cells. Most, or all, of the amino-terminal portion of the glycoprotein, as well as the protein-bound carbohydrate, appears to be located within the lumen of the membrane vesicles. These findings demonstrate that insertion of this membrane protein occurs during or immediately after protein synthesis. The results are consistent with the concepts that the growing membrane protein is extruded across the endoplasmic reticulum membrane amino terminus first and that glycosylation is restricted to the lumenal surface of the membrane. The cell-free system reported here should prove valuable for studying these processes.
 ...
PMID:Membrane assembly in vitro: synthesis, glycosylation, and asymmetric insertion of a transmembrane protein. 19 78

Studies of the synthesis and incorporation of the vesicular stomatitis virus glycoprotein into membranes in a synchronised cell-free system demonstrate a tight coupling between polypeptide synthesis and membrane insertion, as a result of which the nascent chain crosses the membrane. The studies reveal a surprisingly precise sequence by which the nascent chain of this membrane glycoprotein is glycosylated in two steps. These findings have important implications for the mechanisms of membrane assembly.
 ...
PMID:Synchronised transmembrane insertion and glycosylation of a nascent membrane protein. 20 Aug 44

Translation in vitro of the mRNA coding for the vesicular stomatitis virus membrane glycoprotein G in a membrane-free ribosomal extract from HeLa cells allowed the synthesis of only the unglycosylated protein G1 (molecular weight, 63,000). Addition of stripped crude microsomal membranes from HeLa cells resulted in the conversion of G1 to the glycosylated protein G2 (molecular weight, 67,000). The G2 protein synthesized by the reconstructed microsomal membrane/ribosome system was found to be segregated inside the microsomal membrane vesicles and was thus protected from the proteolytic action of trypsin and chymotrypsin. Stripped membranes were required at an early stage of protein synthesis for the synthesized protein to be inserted into the membrane vesicles and to be glycosilated. The segregated protein G2, however, was not completely protected from proteolytic digestion, showing that a portion of the polypeptide chain of about 3000 daltons was present on the cytoplasmic side of the membrane vesicle. Our data thus suggest that, unlike the secretory proteins, the membrane glycoproteins are not completely discharged across the microsomal membranes.
 ...
PMID:In vitro synthesis of vesicular stomatitis virus membrane glycoprotein and insertion into membranes. 20 29

The biosynthesis of a secretory protein and a transmembrane viral glycoprotein are compared by two different experimental approaches. (a) NH2-terminal sequence analysis has been performed on various forms of the transmembrane glycoprotein of vesicular stomatitis virus synthesized in cell-free systems. The sequence data presented demonstrate that the nascent precursor of the glycoprotein contains a "signal sequence" of 16 amino acids at the NH2 terminus, whose sequence is Met-Lys-Cys-Leu-Leu-Tyr-Leu-Ala-Phe-Leu-Phe-Ile-(His-Val-Asn)-Cys. This signal sequence is proteolytically cleaved during the process of insertion into microsomal membranes prior to chain completion. The new NH2 terminus of the inserted, cleaved, and glycosylated membrane protein is located within the lumen of the microsomal vesicles and is identical to that of the authentic glycoprotein from virions. (b) Nascent chain competition experiments were performed between this glycoprotein, bovine pituitary prolactin (a secretory protein), and rabbit globin (a cytosolic protein). It was found that the nascent membrane glycoprotein, but not nascent globin, competed with nascent prolactin for membrane sites involved in the early biosynthetic event of transfer across membranes. These data suggest that an initially common pathway is involved in the biogenesis of secretory proteins and at least one class of integral membrane proteins.
 ...
PMID:A signal sequence for the insertion of a transmembrane glycoprotein. Similarities to the signals of secretory proteins in primary structure and function. 21 27

The components of biological membranes are asymmetrically distributed between the membrane surfaces. Proteins are absolutely asymmetrical in that every copy of a polypeptide chain has the same orientation in the membrane, and lipids are nonabsolutely asymmetrical in that almost every type of lipid is present on both sides of the bilayer, but in different and highly variable amounts. Asymmetry is maintained by lack of transmembrane diffusion. Two types of membrane proteins, called ectoproteins and endoproteins, are distinguished. Biosynthetic pathways for both types of proteins and for membrane lipids are inferred from their topography and distribution in the formed cells. Note added in proof. A cell-free system has now been developed which permits the mechanisms of membrane protein assembly to be studied (108). The membrane glycoprotein of vesicular stomatitis virus has been synthesized by wheat germ ribosomes in the presence of rough endoplasmic reticulum from pancreas. The resulting polypeptide is incorporated into the membrane, spans the lipid bilayer asymmetrically, and is glycosylated (108). The amino terminal portion of this transmembrane protein is found inside the endoplasmic reticulum vesicle, while the carboxyl terminal portion is exposed on the outer surface of the vesicle. Furthermore, addition of the glycoprotein to membranes after protein synthesis does not result in incorporation of the protein into the membrane in the manner described above (108). Consequently, protein synthesis and incorporation into the membrane must be closely coupled. Indeed, using techniques to synchronize the growth of nascent polypeptides, it has been shown (109) that no more than one-fourth of the glycoprotein chain can be made in the absence of membranes and still cross the lipid bilayer when chains are subsequently completed in the presence of membranes. These findings demonstrate directly that the extracytoplasmic portion of an ectoprotein can cross the membrane only during biosynthesis, and not after.
 ...
PMID:Membrane asymmetry. 40 30

A complete set of chimeras was made between the lysosomal membrane glycoprotein LEP100 and the plasma membrane-directed vesicular stomatitis virus G protein, combining a glycosylated lumenal or ectodomain, a single transmembrane domain, and a cytosolic carboxyl-terminal domain. These chimeras, the parent molecules, and a truncated form of LEP100 lacking the transmembrane and cytosolic domains were expressed in mouse L cells. Only LEP100 and chimeras that included the cytosolic 11 amino acid carboxyl terminus of LEP100 were targeted to lysosomes. The other chimeras accumulated in the plasma membrane, and truncated LEP100 was secreted. Chimeras that included the extracellular domain of vesicular stomatitis G protein and the carboxyl terminus of LEP100 were targeted to lysosomes and very rapidly degraded. Therefore, in chimera-expressing cells, virtually all the chimeric molecules were newly synthesized and still in the biosynthesis and lysosomal targeting pathways. The behavior of one of these chimeras was studied in detail. After its processing in the Golgi apparatus, the chimera entered the plasma membrane/endosome compartment and rapidly cycled between the plasma membrane and endosomes before going to lysosomes. In pulse-expression experiments, a large population of chimeric molecules was observed to appear transiently in the plasma membrane by immunofluorescence microscopy. Soon after protein synthesis was inhibited, this surface population disappeared. When lysosomal proteolysis was inhibited, chimeric molecules accumulated in lysosomes. These data suggest that the plasma membrane/early endosome compartment is on the pathway to the lysosomal membrane. This explains why mutations that block endocytosis result in the accumulation of lysosomal membrane proteins in the plasma membrane.
 ...
PMID:The pathway and targeting signal for delivery of the integral membrane glycoprotein LEP100 to lysosomes. 151 88

The processes which transport membrane proteins between compartments of the Golgi apparatus have been reconstituted in vitro using isolated Golgi fractions. This cell-free system allows a detailed analysis of protein transport not possible in intact cells. Transport of the membrane glycoprotein (G protein) of vesicular stomatitis virus (VSV) is measured from a "donor" to an "acceptor" Golgi fraction. The donor Golgi fraction is prepared from VSV-infected Chinese hamster ovary (CHO) mutant cells deficient in the glycosylation enzyme N-acetylglucosamine transferase I. "Acceptor" is prepared from uninfected wild-type CHO cells. Transport is measured by the addition of N-acetylglucosamine to G protein, which can occur only upon movement of G protein from donor to acceptor. Transport requires physiological pH and osmolarity, is dependent on nucleotide triphosphates, and is mediated by proteins both from cytosol and on the Golgi membranes. Protein movement is inhibited by the non-hydrolyzable GTP analogue, GTP gamma S. The process of transport proceeds through the budding, pinching off, targeting, and fusion of transport vesicles. In this system these vesicles are initially coated with a non-clathrin coat and are targeted with this coat intact. Several of the proteins which mediate transport have been characterized, and isolated to homogeneity. The successful development of this assay has led to the formulation of cell free assays for protein transport between other compartments. Comparison of these systems indicates that some common mechanisms of vesicular movement are used in transport between a variety of membrane compartments.
 ...
PMID:Analysis of protein transport through the Golgi in a reconstituted cell-free system. 190 3

Incubation of cultured cells in hypertonic medium and sodium-free medium have been shown to block transport at two different stages along the endocytic pathway. To determine the effects of these treatments on the exocytic pathway, we studied the transport of the membrane glycoprotein of vesicular stomatitis virus (VSV-G) in cells infected with tsO45 mutant virus. This mutant synthesizes a VSV-G that accumulates in the endoplasmic reticulum (ER) when cells are incubated at 39.5 degrees C. In addition, VSV-G accumulates in the post-ER pre-Golgi compartment when cells are incubated at 15 degrees C and in the trans-Golgi network (TGN) when cells are incubated at 18 degrees C. Upon transfer of cells to 32 degrees C in control medium, VSV-G exits each of these compartments and is transported to the cell surface. Incubation in sodium-free medium at 32 degrees C did not block transport from any of these three compartments. In contrast, incubation in hypertonic medium blocked export from the ER, transport from the pre-Golgi compartment to the Golgi complex, and transport from the TGN to the cell surface. Our results, in combination with previous studies, suggest that hypertonic medium blocks at least five distinct transport steps; the three exocytic steps described here, endocytosis from the cell surface, and transport of cell surface proteins into the Golgi complex. This raises the possibility that vesicular transport in different parts of the cell shares common elements that are inhibited by this treatment.
 ...
PMID:Effects of hypertonic and sodium-free medium on transport of a membrane glycoprotein along the secretory pathway in cultured mammalian cells. 199 18


1 2 3 4 5 Next >>