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)

Semliki forest virus and Sindbis virus (Alphaviruses belonging to the togavirus group) grown in BHK-21 cells possessed very low levels of virion-associated protein kinase activity. For comparison, vesicular stomatitis virus, also grown in BHK-21 cells, contained a virion-bound protein kinase which had a specific activity 80 times greater than that of the Alphaviruses. The Alphavirus protein kinase was unmasked by the nonionic detergent Nonidet P-40 but was not activated by cyclic nucleotides. Phosvitin was the best exogenous phosphate acceptor for assaying the viral enzyme in vitro. Phosphoprotein phosphatase activity was also detected in the Alphaviruses. Both in vivo and in vitro, all of the viral structural polypeptides were phosphorylated, and the phosphorylated amino acids were found to be serine and threonine. The viral nucleocapsid protein was about four times more efficient as a phosphate acceptor than were the envelope proteins. From 33 to 50% of the total protein kinase was bound to the viral nucleocapsid, and the specific activity of this enzyme was 4 to 10 times greater than that associated with the viral envelope.
 ...
PMID:Virion-bound protein kinase in Semliki forest and Sindbis viruses. 436 99

Among the protein kinases associated with vesicular stomatitis virus (VSV), one was identified by immunoprecipitation to be pp60src, the transformation-specific product coded for by avian sarcoma virus, or its endogenous cellular homolog. This activity phosphorylated only tyrosine. pp60src was enriched in the membranes, whereas the serine- and threonine-specific kinases were concentrated with viral cores. The content of pp60src in VSV can be manipulated by growing VSV in different host cells. Monolayer baby hamster kidney cells transformed by an avian sarcoma virus produced VSV progeny which contained 7-fold greater pp60src activity than progeny produced by control untransformed or revertant cells. In contrast, suspension cultures of baby hamster kidney cells which produced VSV with increased tyrosine-specific kinase activity did not affect the content of pp60src. When pp60src was specifically increased in cells, the endogenous phosphorylation of tyrosine residues in the VSV matrix M protein was also enhanced, to as much as 20-fold. The phosphorylation of serine or threonine in this protein or in the other VSV phosphoprotein NS was not affected. Cellular tyrosine-specific kinases other than pp60scr did not change the overall phosphorylation pattern of any VSV phosphoproteins. Experiments designed to test the effects of endogenous phosphorylation on the various functions of the M protein failed to detect any significant alterations.
 ...
PMID:Host-dependent phosphorylation and kinase activity associated with vesicular stomatitis virus. 627 33

In a microsome system rendered competent in protein translation by the addition of rabbit reticulocyte lysate, co-translational insertion and glycosylation of N-linked glycoproteins is observed when the appropriate mRNA is supplied. We have utilized this system to examine the ability of acceptor tripeptides of the type Asn-X-Thr/Ser to inhibit co-translational glycosylation. Using endogenous oligosaccharide-lipid as the carbohydrate donor, dog pancreas microsomes efficiently glycosylated N alpha-[3H]Ac-Asn-Leu-Thr-NHCH3 (apparent Km = 100 microM). Glycopeptide formation was essentially complete within 20 min. In the presence of mRNA from vesicular stomatitis virus or chicken ovalbumin, a similar tripeptide, N alpha-Ac-Asn-Leu-Thr-NH2, inhibited co-translational glycosylation. Translocation of the nascent chains was not affected. Thus, in the absence of peptide, all translated G protein was glycosylated and found within the microsomes, whereas in the presence of the peptide a mixture of glycosylated and nonglycosylated G protein was sequestered. Inhibition of nascent chain glycosylation was competitive and not merely the result of oligosaccharide lipid depletion, because preincubation of the microsomes with the peptide followed by its removal did not affect subsequent glycosylation of ovalbumin or G protein. Six derivatives of Asn-Leu-Thr-NH2, three of which were acceptors and three of which were not, were tested for their ability to inhibit co-translational glycosylation. The three acceptor peptides, N alpha-Ac-Asn-Leu-Thr-NH2, N alpha-Oc-Asn-Leu-Thr-NH2, and N alpha-Bz-Asn-Leu-Thr-NH2, effectively inhibited nascent chain glycosylation. In contrast, the three nonacceptors, N alpha-Ac-Gln-Leu-Thr-NH2, N alpha-Ac-Asn(N beta-Me)-Leu-Thr-NH2, and Asn-Leu-Thr-NH2, had no effect. Taken together, these data indicate that the inhibition of co-translational glycosylation by a peptide is dependent on its ability to compete for the active site of the oligosaccharyl transferase.
 ...
PMID:Substrate recognition by oligosaccharyl transferase. Inhibition of co-translational glycosylation by acceptor peptides. 668 31

Our long-term goal is to define the catalytic domains of the L protein subunit of the Sendai virus RNA polymerase. An aberrant polyadenylation phenotype in the vesicular stomatitis virus tsG16 L protein mutant has recently been identified as a phenylalanine to serine change at amino acid 1488 (Hunt and Hutchinson, Virology 193, 786-793, 1993). To test if functional domains are conserved in the L proteins of negative-strand RNA viruses, we attempted to create a similar polyadenylation defect in the Sendai virus L protein. Nine different amino acid substitutions at the analogous site in the Sendai L protein (cysteine at amino acid 1571) were constructed by site-directed mutagenesis of the gene. Each mutant L protein was synthesized and bound to the Sendai P protein to form the P-L polymerase complex. While none of these L mutants exhibited a change in polyadenylation, the single amino acid changes yielded a variety of activities in vitro. Mutants containing valine, leucine, or phenylalanine at amino acid 1571, amino acids found naturally in the L proteins of other paramyxoviruses, yielded polymerases that had biological activity equal to or better than the wild-type (WT) polymerase. Serine or threonine substitutions in the L protein at this position also resulted in polymerases with nearly WT synthetic activity. In contrast, a glycine substitution significantly decreased overall polymerase activity, whereas a tyrosine substitution gave decreased transcription, but virtually no DI genome replication in vitro. The tyrosine-substituted polymerase may be unable to carry out the packaging step of replication, since DI leader RNA synthesis was normal in this mutant. Mutant L proteins with basic arginine or histidine substitutions were inactive in all viral RNA synthesis in vitro, although the polymerase complexes could bind the nucleocapsid template.
 ...
PMID:Alternative amino acids at a single site in the Sendai virus L protein produce multiple defects in RNA synthesis in vitro. 764 61

In order to identify the amino acid sequences responsible for the internalization of the cloned rat brain neurotensin receptor, we carried out site-directed mutagenesis of the cDNA encoding the receptor followed by expression of the receptor into mammalian COS 7 cells. In cells transfected with the full-length neurotensin receptor, 56% of iodinated neurotensin specifically bound to the cells after 60 min of incubation at 37 degrees C was internalized. Deletions made in the third intracellular loop did not affect receptor internalization. By contrast, internalization was reduced to 5% of total in cells in which almost all the carboxyl-terminal tail of the receptor had been deleted (R392stop). In order to determine which part of the tail was responsible for this effect, several Ser and Thr residues were deleted in the carboxyl cytoplasmic sequence of the receptor. Almost all of these receptors were internalized as efficiently as the wild type. Only the form of the neurotensin receptor truncated at Glu-421 (deletion of the last three residues, TLY) produced a significant decrease in the amount of ligand internalized. Finally, point mutations of Thr-422 and Tyr-424 residues to Gly led to an almost complete loss of ligand internalization demonstrating the involvement of these 2 residues in the internalization process. Replacement of the last three amino acids by the cytoplasmic endocytosis signal of the vesicular stomatitis virus did not restore the efficiency of neurotensin receptor internalization. These biochemical results were confirmed by confocal microscopic analysis. Cell transfected with the wild type receptor showed a temperature-dependent intracellular accumulation of a fluorescent analog of neurotensin, whereas cells transfected with a receptor truncated at the carboxyl terminus showed a clustering of the fluorescent peptide at the cell surface.
 ...
PMID:Thr-422 and Tyr-424 residues in the carboxyl terminus are critical for the internalization of the rat neurotensin receptor. 785 3

The matrix (M) protein of vesicular stomatitis virus (VSV) plays a central role in virus assembly by binding the nucleocapsid core to the viral envelope during the budding process. A small percentage of M protein molecules are phosphorylated in vivo, but the role of phosphorylation in M protein function is unknown. Using limited proteolysis, we previously determined the sites of in vivo phosphorylation for VSV M protein to be Thr 31 (and possibly Ser 32) and a site N-terminal to position 19 (Ser 2, Ser 3, or Ser 17) (P. E. Kaptur et al., J. Virol. 66, 5384-5392, 1992). M protein mutants were constructed using site-directed mutagenesis by substituting Ala for Ser or Thr at these sites in the M gene of the San Juan strain of VSV. One mutant had substitutions at the major in vivo phosphorylation site(s) at positions 31 and 32 (M31.32) while two others had additional substitutions at positions 2 and 3 (M2.3.31.32) or at position 17 (M17.31.32). Mutant M proteins were expressed in BHK cells using the vaccinia/T7 system, radiolabeled with 32Pi, and then analyzed for 32P content by PAGE and autoradiography. The data show that the site of phosphorylation near the N-terminus is at Ser 2 or 3 and not Ser 17. Further, Ser 38 was not phosphorylated. Mutation of the major phosphorylation site enhanced phosphorylation at alternative sites in the M protein C-terminal to amino acid 43 and at Ser residues 2 and 3. Mutant M proteins were tested for their ability to complement growth of the temperature-sensitive M protein mutant virus tsO23 at the nonpermissive temperature. Mutant M2.3.31.32 was further tested for its ability to assemble into VSV-defective interfering (DI) particles, using a replication system in which the DI genome and all five VSV proteins were expressed from plasmid DNA. Assembly of tsO23 virions or DI particles in the presence of mutant M proteins was similar to that observed for wild-type M proteins. These data indicate that phosphorylation of M protein at the major in vivo sites is not essential for virus assembly.
 ...
PMID:Assembly functions of vesicular stomatitis virus matrix protein are not disrupted by mutations at major sites of phosphorylation. 785 2

TsW16B is a temperature-sensitive mutant of vesicular stomatitis virus. Others have shown that it is temperature-sensitive for replication in vivo and for transcription in vitro and that these phenotypes are probably due to mutation of the N (nucleocapsid) gene. Five independent revertants were isolated from tsW16B based on their ability to grow at 39 degrees C. The thermosensitivity of in vitro transcription by these revertants was similar to that of the wild-type virus [wt(HR)] from which tsW16B was derived. Fractionation-reconstitution studies of two revertants indicated that the reversion was in the N or P (phosphoprotein) gene. The N and P genes of wt(HR), tsW16B, and these two revertants were sequenced. There were no differences between the P genes. Comparison of the predicted N protein sequences of wt(HR), tsW16B and the two revertants indicated that the growth and in vitro transcription phenotypes of tsW16B were due to a change of amino acid residue 238 from threonine to isoleucine. The amino acid at position 238 in the other three revertants also showed an exact reversion to threonine. Amino acid residue 238 lies in a domain of the N protein which is highly conserved among vesiculoviruses.
 ...
PMID:Identification of an amino acid change that affects N protein function in vesicular stomatitis virus. 799 52

A class of integral membrane glycoproteins specific to lysosomes has been identified, and they are classified into two separate groups depending on whether or not their cytoplasmic sequence contains a tyrosine residue. Lamp-1 and lamp-2 have a tyrosine-containing motif in their cytoplasmic segments, and this motif was found to direct the glycoproteins to lysosomes. Limp II glycoprotein, on the other hand, lacks a tyrosine in its cytoplasmic segment and it must be directed to lysosomes by a different signal (Fukuda, M. (1991) J. Biol. Chem. 266, 21327-21330). In order to elucidate the targeting signal of Limp II, a cDNA encoding its cytoplasmic segment was fused with a reporter molecule, a chimeric protein of human gonadotropin alpha chain-vesicular stomatitis G-protein transmembrane. After various mutations its expression was examined by immunofluorescence. First it was shown that a chimeric protein with a Limp II wild-type tail is transported to lysosomes. Deletion of the three amino acids of the cytoplasmic tail at the carboxyl terminus abolished this sorting to lysosomes. Substitution of individual amino acids revealed that the Leu-Ile motif in the Leu-Ile-Arg-Thr sequence at the carboxyl terminus is crucial to the sorting signal. When this motif was brought closer to the transmembrane domain by deletion of nine amino acids next to the transmembrane domain, this sorting function was abolished. In addition, substitution of alanine for the serine, which is at 5 residues from the transmembrane also abolished the sorting capacity, although there was no evidence that the phosphorylation of serine is involved in sorting. Altered proteins that were not transported to lysosomes were found to accumulate at the cell surface and, unlike proteins with a wild-type cytoplasmic tail, were unable to undergo endocytosis. These results indicate that the carboxyl-terminal amino acid sequence, including the Leu-Ile motif and the sequence that connects the motif to the transmembrane domain, is critical for the sorting of Limp II to lysosomes.
 ...
PMID:Lysosomal targeting of Limp II membrane glycoprotein requires a novel Leu-Ile motif at a particular position in its cytoplasmic tail. 810 3

Certain large DNA viruses (e.g. herpesviruses and poxviruses) encode proteins related to cellular protein-serine/threonine kinases, and Hepatitis B virus and vesicular stomatitis virus may encode structurally different protein kinases. Other viruses activate cellular protein kinases, e.g. interferon-induced eukaryotic initiation factor-2 kinase, growth factor-induced kinases and protein kinases that regulate mitosis. Protein phosphatases are encoded by vaccinia virus and bacteriophage lambda and must also play a role in viral infection--as do cellular protein phosphatases. The functions of many of these viral enzymes remain to be determined, but they represent possible new targets for anti-viral therapy.
 ...
PMID:Viral protein kinases and protein phosphatases. 830 96

Human MxA protein is an interferon-induced 76-kDa GTPase that exhibits antiviral activity against several RNA viruses. Wild-type MxA accumulates in the cytoplasm of cells. TMxA, a modified form of wild-type MxA carrying a foreign nuclear localization signal, accumulates in the cell nucleus. Here we show that MxA protein is translocated into the nucleus together with TMxA when both proteins are expressed simultaneously in the same cell, demonstrating that MxA molecules form tight complexes in living cells. To define domains important for MxA-MxA interaction and antiviral function in vivo, we expressed mutant forms of MxA together with wild-type MxA or TMxA in appropriate cells and analyzed subcellular localization and interfering effects. An MxA deletion mutant, MxA(359-572), formed heterooligomers with TMxA and was translocated to the nucleus, indicating that the region between amino acid positions 359 and 572 contains an interaction domain which is critical for oligomerization of MxA proteins. Mutant T103A with threonine at position 103 replaced by alanine had lost both GTPase and antiviral activities. T103A exhibited a dominant-interfering effect on the antiviral activity of wild-type MxA rendering MxA-expressing cells susceptible to infection with influenza A virus, Thogoto virus, and vesicular stomatitis virus. To determine which sequences are critical for the dominant-negative effect of T103A, we expressed truncated forms of T103A together with wild-type protein. A C-terminal deletion mutant lacking the last 90 amino acids had lost interfering capacity, indicating that an intact C terminus was required. Surprisingly, a truncated version of MxA representing only the C-terminal half of the molecule exerted also a dominant-negative effect on wild-type function, demonstrating that sequences in the C-terminal moiety of MxA are necessary and sufficient for interference. However, all MxA mutants formed hetero-oligomers with TMxA and were translocated to the nucleus, indicating that physical interaction alone is not sufficient for disturbing wild-type function. We propose that dominant-negative mutants directly influence wild-type activity within hetero-oligomers or else compete with wild-type MxA for a cellular or viral target.
 ...
PMID:Dominant-negative mutants of human MxA protein: domains in the carboxy-terminal moiety are important for oligomerization and antiviral activity. 906 Jun 10


<< Previous 1 2 3 4 Next >>