Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two mutants of Sindbis virus have been isolated which grow inefficiently at 34.5 degrees C in mosquito cells yet replicate normally in chicken embryo fibroblast cells at the same temperature. In addition, these mutants exhibit temperature-sensitive growth in both cell types and are RNA- at the nonpermissive temperatures (K.J. Kowal and V. Stollar, Virology 114:140-148, 1981). To clarify the basis of this host restriction, we have mapped the causal mutations for these temperature-dependent, host-restricted mutants. Functional mapping and sequence analysis of the mutant cDNAs revealed several mutations which mapped to the amino terminus of nsP4, the putative polymerase subunit of the viral RNA replicase. These mutations resulted in the following amino acid changes in nsP4: leucine to valine at residue 48, aspartate to glycine at residue 142, and proline to arginine at residue 187. Virus containing any of these mutations was restricted in its ability to replicate in mosquito but not chicken embryo fibroblast cells at 34.5 degrees C. In addition to its temperature-dependent, host-restricted phenotype, virus derived from one cDNA clone also exhibited decreased levels of nsP34 and nsP4 yet contained only a silent change in its genome. This C-to-U mutation occurred at nucleotide 5751, the first nucleotide after the opal termination codon separating nsP3 and nsP4. Our results suggest that this substitution decreases readthrough of the opal codon and diminishes production of nsP34 and nsP4. Such a decrease in synthesis rates might lead to levels of these products which are insufficient for viral RNA replication in mosquito cells at the higher temperature. This work provides the first evidence that nsP4 function can be strongly influenced by the host environment.
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PMID:Mutations which alter the level or structure of nsP4 can affect the efficiency of Sindbis virus replication in a host-dependent manner. 215 58

1. Aminoacyl-transfer-RNA synthetase activity in extracts prepared from tobacco leaf was increased 3-5-fold when sodium thioglycollate (30mm) and magnesium chloride (16mm) were included in the extraction medium. Omitting sucrose (0.45m) from the extraction medium did not alter the activity. 2. Activity was a linear function of enzyme concentration up to 1 disk (30mg. fresh wt.)/ml. and was not affected by dialysis at any concentration. 3. Activity increased about 13-fold above control values when a mixture of 21 amino acids and amides (1mm) was added to the reaction mixture. 4. Under the conditions used in the standard assay for aminoacyl-transfer-RNA synthetase activity K(m) (ATP) was 0.65mm and K(m) (l-amino acids) was 70mum. 5. Activity above the control value was found with all amino acids and amides tested except alanine, arginine, glutamic acid, glutamine and hydroxyproline. Activity was highest with leucine, isoleucine, valine, cysteine and histidine. Total activity with a mixture of 21 amino acids and amides was 20% lower than the total activity of the enzymes assayed separately.
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PMID:The extraction and assay of aminoacyl-transfer-ribonucleic acid synthetases of tobacco leaf. 422 1

The outer surface lipoproteins of Borrelia burgdorferi, OspA and OspB, stimulate the production of nitric oxide (NO) by murine bone marrow-derived macrophages from BALB/c, C3H/HeN, and C3H/HeJ mice. Gamma interferon (IFN-gamma) caused a three- to fivefold enhancement of this production of NO, and the L-arginine analog N-guanidino-monomethyl L-arginine inhibited it. Activation of transcription of the inducible NO synthase gene in stimulated macrophages was demonstrated by reverse transcriptase rapid PCR. Although IFN-gamma increased the amount of NO produced in macrophage cultures, it did not cause transcription of the inducible NO synthase gene greater than that seen with the Borrelia proteins. OspA and OspB also induced the production of high levels (40 to 150 ng/ml) of IFN-gamma in cultures of macrophages incubated with interleukin-2 (IL-2)-elicited cells from normal (T and NK cells) and scid (NK cells) mice but not in macrophages or IL-2-elicited cells cultured individually. This suggests that OspA stimulated macrophage production of cytokines, which, in turn, stimulated the production of IFN-gamma by NK and T cells. Reverse transcriptase rapid PCR demonstrated that OspA and sonicated B. burgdorferi stimulated production of several inflammatory cytokines in macrophage cultures, including IL-1, IL-6, IL-12, IFN-beta, and tumor necrosis factor alpha. As tumor necrosis factor alpha, IFN-beta, and IL-12 are potent activators of IFN-gamma production by T and NK cells, their presence in these cocultures could be responsible for the IFN-gamma production. Lymphocytes from infected C3H mice also produced IFN-gamma when stimulated with B. burgdorferi; thus, immune cells may also modulate NO responses. The generation of NO during infection with B. burgdorferi may be important, as NO has potent antimicrobial properties. NO can also be involved in pathological inflammatory processes in which its generation is detrimental to the host. Thus, the colocalization of B. burgdorferi lipoproteins, NO-producing cells, and regulatory cytokines may determine the outcome of infection.
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PMID:Outer surface lipoproteins of Borrelia burgdorferi stimulate nitric oxide production by the cytokine-inducible pathway. 752 Apr 17

Although the third component of complement, C3, has been isolated and its primary structure determined from most living classes of vertebrate, limited information is available on its structure and function for aves, which represent a significant stage in complement evolution. In this study, we present the complete cDNA sequence of chicken C3, the cDNA sequences of the thioester region for two chicken alpha 2-macroglobulin (alpha 2M)-related proteins, a simplified method for purifying chicken C3, and an analysis of the C3 convertase and factor I-mediated cleavages in chicken C3. Using the reverse-transcriptase PCR, with degenerate oligonucleotide primers derived from two conserved C3 sequences (GCGEQN/TM, TWLTAY/FV) and liver mRNA as template, we isolated three distinct 220-bp PCR products, one with a high degree of sequence similarity to C3 and two to alpha 2M and pregnancy zone protein from other species. The complete cDNA sequence of chicken C3 was obtained by screening a chicken liver lambda gt10 library with the C3 PCR product and probes from the 5' end of the partial-length C3 clones. The obtained sequence is in complete agreement with the protein sequence of several tryptic peptides of purified chicken C3. Chicken pro-C3 consists of an 18-residue putative signal peptide, a 640-residue beta-chain (70 kDa), a 989-residue alpha-chain (111 kDa), and an RKRR linker region. It contains an internal thioester and three potential N-glycosylation sites, all in the alpha-chain. The convertase cleavage site, predicted to be Arg-Ser, was confirmed by sequencing the zymosan-bound C3 fragments generated upon complement activation. NH2-terminal sequencing of the purified C3 chains showed that 1) pro-C3 is indeed cleaved at the RKRR linker sequence to generate the mature two-chain molecule, and 2) the beta-chain of chicken C3 is blocked. The deduced amino acid sequence shows 54, 54, 54, 53, 52, 57, and 55% amino acid identities to human, mouse, rat, guinea pig, rabbit, cobra, and Xenopus C3, respectively, and an identity of 44, 31, and 33% to trout, hagfish, and lamprey C3, respectively. The identities to human C4, C5, and alpha 2M are 31, 29 and 23%, respectively. A phylogenetic tree for C3, C4, C5, and alpha 2M-related proteins was constructed based on the sequence data and is discussed.
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PMID:Isolation, primary structure, and evolution of the third component of chicken complement and evidence for a new member of the alpha 2-macroglobulin family. 753 62

Four individuals have been identified, within a single family, who lack phagocyte expression of the high affinity type I IgG receptor (CD64). As a result, their monocytes are unable to support mouse IgG2a anti-CD3-induced T cell mitogenesis (nonresponder individuals). Southern blotting proved all three human Fc gamma receptor I (hFc gamma RI) genes to be present in nonresponders without major structural changes. Nucleotide sequencing showed identical hFc gamma RIA promoter regions in all individuals. At the message level, a distinct difference was noted between monocytes from control (responder) donors and from nonresponders. Both a 1.7- and 1.6-kb message were found in responders, whereas in nonresponders only the 1.6-kb species was detectable. Reverse transcriptase-PCR analyses showed the hFc gamma RIa transcript (encoding a receptor with three extracellular Ig-like domains) to be present at a approximately 15- to 20-fold lower level in nonresponder monocytes. Importantly, we found a single nucleotide difference (C --> T) within the extracellular domain exon 1-encoding region of hFc gamma RIA in nonresponders, resulting in the change of codon 92 (encoding an arginine) into a termination codon. This change likely affects mRNA stability and, thereby, leads to undetectable expression of phagocyte-hFc gamma RIa. Despite this defect, these individuals are apparently healthy, suggesting that hFc gamma RIa is dispensable for phagocyte functioning.
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PMID:Molecular basis for a familial defect in phagocyte expression of IgG receptor I (CD64). 753 86

Nitric oxide (NO) has been implicated in the pathogenesis of several inflammatory diseases. In the present study, we investigated the potential role of NO in an ocular model of inflammation, endotoxin-induced uveitis (EIU), in Lewis rats. Injection of LPS in one footpad induces severe uveitis after 16 h, which is accompanied by an increase of NO in the aqueous and vitreous humors, as evaluated by nitrite assay. Reverse transcriptase-PCR experiments reveal a large increase of inducible NO synthase (iNOS) mRNA in the iris/ciliary body, from 2 to 24 h after LPS treatment. In the retina, maximal increase of iNOS mRNA was detected 16 h after LPS treatment. Two i.p. injections of the NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), which inhibits nitrite release in the aqueous and vitreous humors, profoundly reduce clinical and histologic inflammation in EIU rats. These results implicate the NO pathway in the pathogenesis of EIU and demonstrate the possibility of modulating this inflammatory disease by injection of a NOS inhibitor.
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PMID:Increased nitric oxide production in endotoxin-induced uveitis. Reduction of uveitis by an inhibitor of nitric oxide synthase. 753 24

The sequence of the entire genome of citrus tristeza virus (CTV), Florida isolate T36, was completed. The 19,296-nt CTV genome encodes 12 open reading frames (ORFs) potentially coding for at least 17 protein products. The 5'-proximal ORF 1a starts at nucleotide 108 and encodes a large polyprotein with calculated MW of 349 kDa containing domains characteristic of (from 5' to 3') two papain-like proteases (P-PRO), a methyltransferase (MT), and a helicase (HEL). Alignment of the putative P-PRO sequences of CTV with the related proteases of beet yellows closterovirus (BYV) and potyviruses allowed the prediction of catalytic cysteine and histidine residues as well as two cleavage sites, namely Val-Gly/Gly for the 5' proximal P-PRO domain and Met-Gly/Gly for the 5' distal P-PRO domain. The autoproteolytic cleavage of the polyprotein at these sites would release two N-terminal leader proteins of 54 and 55 kDa, respectively, and a 240-kDa C-terminal fragment containing MT and HEL domains. The apparent duplication of the leader domain distinguishes CTV from BYV and accounts for most of the size increase in the ORF 1a product of CTV. The downstream ORF 1b encodes a 57-kDa putative RNA-dependent RNA polymerase (RdRp), which is probably expressed via a +1 ribosomal frameshift. Sequence analysis of the frameshift region suggests that this +1 frameshift probably occurs at a rare arginine codon CGG and that elements of the RNA secondary structure are unlikely to be involved in this process. The complete polyprotein resulting from this frameshift event has a calculated MW of 401 kDa and after cleavage of the two N-terminal leaders would yield a 292-kDa protein containing the MT, HEL, and RdRp domains. Phylogenetic analysis of the three replication-associated domains, MT, HEL, and RdRp, indicates that CTV and BYV form a separate closterovirus lineage within the alpha-like supergroup of positive-strand RNA viruses. Two gene blocks or modules can be easily identified in the CTV genome. The first includes the replicative MT, HEL, and RdRp genes and is conserved throughout the entire alpha-like superfamily. The second block consists of five ORFs, 3 to 7, conserved among closteroviruses, including genes for the CTV homolog of HSP70 proteins and a duplicate of the coat protein gene. The 3'-terminal ORFs 8 to 11 encode a putative RNA-binding protein (ORF 11), and three proteins with unknown functions; this gene array is poorly conserved among closteroviruses.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Complete sequence of the citrus tristeza virus RNA genome. 774 24

Hepatitis A virus (HAV) cDNAs encoding the P3 region proteins were expressed in vivo and in vitro to characterize the HAV 3D protein and to identify the cleavage site between 3C and 3D. Protein coding sequences were placed under control of a T7 promoter and an EMCV translational initiation signal. T7 RNA polymerase was provided by simultaneous infection of transfected BS-C-1 cells with a recombinant vaccinia virus vTF7-3 (T. R. Fuerst et al., Proc. Natl. Acad. Sci. USA 83, 8122-8126, 1986). Efficient synthesis and processing of P3 proteins occurred to yield 3CD (78 kDa), 3D (54 kDa), 3ABC (33 kDa), 3BC (25 kDa), and 3C (23 kDa). Similar products were produced by translation of T7 transcripts in a rabbit reticulocyte lysate in vitro. The 3C/D cleavage site was mapped by comparing the mobility of 3D in SDS-PAGE with 3D proteins engineered to begin at each of the two proposed cleavage sites; in addition, direct N-terminal sequencing of radiolabeled 3D protein from translation in vitro was performed. The results showed that 3D was formed by cleavage at the glutamine-arginine (Q/R) pair at position 1738 and 1739 of the HAV polyprotein. HAV 3D protein produced by autocatalytic cleavage of P3 precursor proteins in BS-C-1 cells is virtually completely insoluble and sediments after low-speed centrifugation. This is in contrast to the poliovirus 3D protein, produced from a similar construct, a significant portion of which remains soluble. Extracts containing the poliovirus 3D protein manifested high levels of RNA-dependent RNA polymerase activity, whereas those containing the HAV 3D protein showed no detectable activity by the same assay.
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PMID:Expression of hepatitis A virus precursor protein P3 in vivo and in vitro: polyprotein processing of the 3CD cleavage site. 829 Dec 34

We have studied the actions of the proteinase-activated-receptor-2 (PAR2)-activating polypeptide, SLIGRL-NH2 (SLI-NH2), in rat aorta and in gastric longitudinal muscle preparations. In the phenylephrine-precontracted aorta preparation, SLI-NH2 caused an endothelium-dependent relaxation that mimicked the action of low concentrations (0.5 U/mL) of trypsin and that was blocked by the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester. In endothelium-free aorta ring preparation, SLI-NH2 caused neither a relaxation nor a contraction. In the gastric longitudinal muscle preparation, SLI-NH2 caused a transient contraction that mimicked the action of trypsin (0.5 U/mL) and that was sensitive to inhibitors of cyclooxygenase (indomethacin) and tyrosine kinase (genistein). Further, using a reverse-transcriptase - polymerase chain reaction (RT-PCR) approach we detected, in both assay tissues, mRNA for the rat PAR2 receptor, and we ascertained, using a cloned receptor cDNA obtained from a rat intestinal cDNA library, that the putative N-terminal activating peptide sequence of the rat PAR2 receptor (SLIGRL) is identical with the one previously cloned from murine tissue. We concluded that, like the thrombin receptor, the PAR2 receptor may play a pathophysiologic role in the regulation of vascular and gastric smooth muscle contractility.
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PMID:Detection of functional receptors for the proteinase-activated-receptor-2-activating polypeptide, SLIGRL-NH2, in rat vascular and gastric smooth muscle. 856 91

In a previous study, we identified a lysine (Lys)-binding-defective form of human lipoprotein(a) and attributed this defect to the presence of a Trp72-->Arg mutation in apolipoprotein(a) [apo(a)] kringle IV-10. To document this relationship, we expressed both wild-type (wt) and mutant (mut) forms of kringle IV-10 in Escherichia coli (nonglycosylated form) and Chinese hamster ovary (CHO) cells (glycosylated form). The Arg72 mut was prepared by introducing the T-->A mutation in apo(a) kringle IV-10 amplified from human liver mRNA by the reverse-transcriptase polymerase chain reaction technique. All expressed kringles were tested for their ability to bind Lys and plasmin-modified fibrinogen (PM-fibrinogen). wt kringle IV-10 expressed in both E coli and CHO cells bound to Lys-Sepharose with comparable affinity. In contrast, the Arg72 mut expressed in both systems exhibited no Lys-binding capacity. Moreover, the wt kringle IV-10 expressed in both systems bound to PM-fibrinogen and exhibited two binding components, one Lys mediated (inhibitable by epsilon-amino-n-caproic acid) and one Lys insensitive, occurring in about the same proportions. Only the latter type of binding was present in the Arg72 mut expressed in E coli. We conclude that kringle IV-10 of human apo(a) has Lys- and PM-fibrinogen-binding capacities that are independent of glycosylation and require the presence of Trp72, one of the seven amino acids that constitute the Lys-binding site of kringle IV-10. Our results also show that the binding of kringle IV-10 to PM- fibrinogen is more complex than that to Lys, in that the former requires an additional binding site or sites outside the Lys-binding site.
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PMID:Lys and fibrinogen binding of wild-type (Trp72) and mutant (Arg72) human apo(a) kringle IV-10 expressed in E coli and CHO cells. 863 Jun 65


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