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:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Signal recognition particle (SRP) induces elongation arrest of nascent presecretory proteins as the signal peptide protrudes from the large ribosomal subunit. To examine the relationship between the size of the precursor and extent of SRP mediated inhibition of polypeptide chain elongation, we performed in vitro translation experiments in the presence of SRP using a series of truncated preproinsulin mRNA molecules. These precursors possessed the same NH2 terminus as native preproinsulin followed by progressively shorter COOH termini. SRP inhibited translation of precursors as short as 64 amino acids in length, however, the extent of inhibition diminished for shorter precursors. This correlated with a reduction in the time required for ribosomes to transit through the mRNA encoding the shortened precursors. By exploiting a chimeric protein comprising the first 71 residues of preproinsulin fused to the bacterial cytoplasmic enzyme chloramphenicol acetyltransferase, we demonstrate that the largest size a nascent chain can reach and still be susceptible to SRP-mediated elongation arrest is approximately 17 kDa. Our data support the model that SRP binding to the signal peptide is a reversible process even in the absence of microsomal membranes, and that SRP can arrest polypeptide chain elongation at multiple stages during translation.
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PMID:Translocation of preproinsulin across the endoplasmic reticulum membrane. The relationship between nascent polypeptide size and extent of signal recognition particle-mediated inhibition of protein synthesis. 131 69

Analysis of the p50 and p65 subunits of the NF-kappa B transcription factor complex has revealed that both proteins can interact with related DNA sequences through either homo- or heterodimer formation. In addition, the product of the proto-oncogene c-rel can bind to similar DNA motifs by itself or as a heterodimer with p50 or p65. However, these studies have used a limited number of known kappa B DNA motifs, and the question of the optimal DNA sequences preferred by each homodimer has not been addressed. Using purified recombinant p50, p65, and c-Rel proteins, optimal DNA-binding motifs were selected from a pool of random oligonucleotides. Alignment of the selected sequences allowed us to predict a consensus sequence for binding of the individual homodimeric Rel-related proteins, and DNA-protein binding analysis of the selected DNA sequences revealed sequence specificity of the proteins. Contrary to previous assumptions, we observed that p65 homodimers can interact with a subset of DNA sequences not recognized by p50 homodimers. Differential binding affinities were also obtained with p50- and c-Rel-selected sequences. Using either a p50- or p65-selected kappa B motif, which displayed differential binding with respect to the other protein, little to no binding was observed with the heterodimeric NF-kappa B complex. Similarly, in transfection experiments in which the selective kappa B binding sites were used to drive the expression of a chloramphenicol acetyltransferase reporter construct, the p65- and p50-selected motifs were activated only in the presence of p65 and p50/65 (a chimeric protein with the p50 DNA binding domain and p65 activation domain) expression vectors, respectively, and neither demonstrated a significant response to stimuli that induce NF-kappa B activity. These findings demonstrate that interaction of both subunits of the heterodimeric NF-kappa B complex with DNA is required for DNA binding and transcriptional activation and suggest that transcriptional activation mediated by the individual rel-related proteins will differ dramatically, depending on the specific kappa B motifs present.
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PMID:Selection of optimal kappa B/Rel DNA-binding motifs: interaction of both subunits of NF-kappa B with DNA is required for transcriptional activation. 140 30

Previous studies have shown that the molecules of P protein associated with transcriptionally active Sendai virus nucleocapsids are arranged in discrete clusters. Our study investigates whether or not this localized distribution is due to the existence of only a few P protein binding sites on the nucleocapsid core. We used immunoelectron microscopy to examine whether additional P proteins could bind at locations between the groups of endogenous P proteins. To differentiate between endogenous and added proteins, we constructed a recombinant gene which instructs the in vitro synthesis of a chimeric protein containing the carboxyl-terminal nucleocapsid-binding region of P protein, fused to chloramphenicol acetyltransferase (CAT). Immunogold labelling, using an antibody to the CAT moiety, revealed at the electron microscope level, that the chimeric product bound to nucleocapsids at many sites located over the entire length of the nucleocapsid. This indicated that the localized distribution of P protein molecules is not due to a limited number of P protein binding sites on the nucleocapsid core.
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PMID:Localization of P protein binding sites on the Sendai virus nucleocapsid. 215 9

Previously the receptor recognition domain of the reovirus serotype 3 (T3) cell attachment protein (sigma 1) was mapped to the C-terminal half of the protein using deletion mutagenesis of the reovirus S1 gene. A similar approach has been adopted in the present study to map the domain on T3 sigma 1 that is responsible for incorporation into the virion (i.e., the anchoring domain). Restriction enzymes which divide the T3 S1 cDNA into four segments (5'-I-II-III-IV-3') of similar size were used to generate four mutants, each with a particular segment deleted. The mutants were cloned into SV40 expression vectors and used to transfect COS-1 cells which were subsequently with reovirus serotype 1. Progeny viral particles with truncated T3 sigma 1 proteins incorporated were then identified by radioimmunoprecipitation with a serotype-specific anti-T3 sigma 1 serum. It was found that the mutant lacking I (mutant dl) was totally incapable of being incorporated into the virion, whereas the mutant lacking domain II (mutant dII) was incorporated efficiently. Due to altered antigenicities of the mutants lacking domain III (mutant dIII) or domain IV (mutant dIV), incorporation of these two proteins into virions was less detectable using the above assay. Evidence that domain I (the N-terminal 121 amino acids) alone dictates the incorporation of sigma 1 into the virion came from the subsequent demonstration that a chimeric protein containing domain I fused to chloramphenicol acetyltransferase (CAT) was incorporated into the virion (detectable with an anti-CAT serum) as efficiently as the full-length sigma 1 protein.
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PMID:The N-terminal quarter of reovirus cell attachment protein sigma 1 possesses intrinsic virion-anchoring function. 221 43

A reverse genetics approach which allows the generation of infectious defective rabies virus (RV) particles entirely from plasmid-encoded genomes and proteins (K.-K. Conzelmann and M. Schnell, J. Virol. 68:713-719, 1994) was used to investigate the ability of a heterologous lyssavirus glycoprotein (G) and chimeric G constructs to function in the formation of infectious RV-like particles. Virions containing a chloramphenicol acetyltransferase (CAT) reporter gene (SDI-CAT) were generated in cells simultaneously expressing the genomic RNA analog, the RV N, P, M, and L proteins, and engineered G constructs from transfected plasmids. The infectivity of particles was determined by a CAT assay after passage to helper virus-infected cells. The heterologous G protein from Eth-16 virus (Mokola virus, lyssavirus serotype 3) as well as a construct in which the ectodomain of RV G was fused to the cytoplasmic and transmembrane domains of the Eth-16 virus G rescued infectious SDI-CAT particles. In contrast, a chimeric protein composed of the amino-terminal half of the Eth-16 virus G and the carboxy-terminal half of RV G failed to produce infectious particles. Site-directed mutagenesis was used to convert the antigenic site III of RV G to the corresponding sequence of Eth-16 G. This chimeric protein rescued infectious SDI-CAT particles as efficiently as RV G. Virions containing the chimeric protein were specifically neutralized by an anti-Eth-16 virus serum and escaped neutralization by a monoclonal antibody directed against RV antigenic site III. The results show that entire structural domains as well as short surface epitopes of lyssavirus G proteins may be exchanged without affecting the structure required to mediate infection of cells.
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PMID:Mokola virus glycoprotein and chimeric proteins can replace rabies virus glycoprotein in the rescue of infectious defective rabies virus particles. 785 76

Nucleolin (713 aa), a major nucleolar protein, presents two structural domains: a N-terminus implicated in interaction with chromatin and a C-terminus containing four RNA-binding domains (RRMs) and a glycine/arginine-rich domain mainly involved in pre-rRNA packaging. Furthermore, nucleolin was shown to shuttle between cytoplasm and nucleolus. To get an insight on the nature of nuclear and nucleolar localization signals, a set of nucleolin deletion mutants in fusion with the prokaryotic chloramphenicol acetyltransferase (CAT) were constructed, and the resulting chimeric proteins were recognized by anti-CAT antibodies. First, a nuclear location signal bipartite and composed of two short basic stretches separated by eleven residues was characterized. Deletion of either motifs renders the protein cytoplasmic. Second, by deleting one or more domains implicated in nucleolin association either with DNA, RNA, or proteins, we demonstrated that nucleolar accumulation requires, in addition to the nuclear localization sequence, at least two of the five RRMs in presence or absence of N-terminus. However, in presence of only one RRM the N-terminus allowed a partial targeting of the chimeric protein to the nucleolus.
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PMID:Determination of the functional domains involved in nucleolar targeting of nucleolin. 816 7

Leukemia-inhibitory factor (LIF) is a neuropoietin able to regulate the differentiation and the survival of many cell types, which include some neuronal populations. The present study describes the genetic construction, expression, purification and properties of a diphtheria-toxin-related LIF gene fusion in which the native receptor-binding domain of diphtheria toxin was replaced with a gene encoding human LIF. The fusion protein expressed from the chimeric tox gene was designated DT-(1-389)-LIF-(2-184)-peptide. This fusion protein has a deduced molecular mass of 65980 Da and is formed by fusion of the first 389 amino acids of diphtheria toxin to amino acids 2-184 of mature human LIF, using a linker of 34 amino acids that includes six consecutive histidine residues. The latter span allows for single-step purification of the fusion protein by Ni(2+)-resin affinity chromatography. This linker provides a high degree of flexibility between the diphtheria toxin and LIF domains, thereby permitting aggregation-free refolding of the chimeric protein while bound to the affinity column. Both LIF and DT-(1-389)-LIF-(2-184)-peptide induced the phosphorylation of CLIP1 and CLIP2 in LIF-responsive neuroblastoma SH-N-BE cells. DT-(1-389)-LIF-(2-184)-peptide was selectively cytotoxic for cultured neuroblastoma cells bearing the LIF receptor, and for sympathetic neurons. The cytotoxic action of DT-(1-389)-LIF-(2-184)-peptide, like that of native diphtheria toxin, required receptor-mediated endocytosis, passage through an acidic compartment, and delivery of an ADP-ribosyltransferase to the cytosol of target cells. The latter point was confirmed by the fact that, while both LIF and DT-(1-389)-LIF-(2-184)-peptide increased c-fos mRNA expression in SH-N-BE cells, only LIF induced proenkephalin and c-fos promoter activities in cells transiently transfected with c-fos-chloramphenicol acetyltransferase and proenkephalin-chloramphenicol acetyltransferase fusion genes. Mutational analysis suggested that the C-terminal helix (helix D) of human LIF may, in part, constitute or contribute to the active site for LIF receptor binding and cell activation. The cytotoxic properties of DT-(1-389)-LIF-(2-184)-peptide may be useful in selectively depleting neuronal and immune cell populations that express the LIF beta receptor.
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PMID:Synthesis, cytotoxic properties and effects on early and late gene induction of a chimeric diphtheria toxin-leukemia-inhibitory factor protein. 891 49

Myxoid liposarcomas are characterized by t(12; 16)(q13;p11) translocation and expression of TLS/ FUS-CHOP chimeric transcripts (types I to III). Among these, the type II transcript is expressed in the majority of cases of myxoid and round cell liposarcoma. To investigate the function of the type II chimeric protein, we obtained stable transformants of ST-13, a murine preadipocytic cell line, which express TLS/FUS-CHOP type II protein (ST-TC) or CHOP protein (ST-C) as well as vector-transfected controls (ST-V). ST-TC and ST-C cells showed almost complete or partial resistance to adipogenic conversion by insulin and thiazolidinedione, respectively. Induction by adipogenic stimulation of the adipocytic genes such as C/EBP alpha, aP2, and adipsin was almost totally suppressed in the ST-TC cells, whereas in ST-C cells C/EBP alpha alone was induced without induction of aP2 and adipsin. Transcriptional suppression of the C/EBP alpha gene in ST-TC cells was suggested by the results of chloramphenicol acetyltransferase (CAT) assay showing a significantly lower C/EBP alpha promoter activity compared with findings in ST-C and ST-V cells. Failure to rescue adipogenic conversion by ectopic expression of C/EBP alpha in ST-TC cells suggested a functional impairment of C/EBP alpha to induce expression of downstream genes. TLS/FUS-CHOP type II protein showed transforming activity, as evidenced by loss of contact inhibition of growth, anchorage-independent growth in soft agar, and tumor formation in nude mice, showing typical histological features of myxoid liposarcoma seen in humans. These findings suggest important roles for TLS/FUS-CHOP type II protein in the oncogenesis of myxoid liposarcoma.
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PMID:Oncogenic transformation and inhibition of adipocytic conversion of preadipocytes by TLS/FUS-CHOP type II chimeric protein. 928 22

The human immunodeficiency virus type 1 Vpr is a virion-associated protein that is incorporated in trans into viral particles, presumably via an interaction with the p6 domain of the Gag polyprotein precursor. Recently, several studies demonstrated that Vpr fusion proteins could be used as intravirion inactivating agents. In this study, we compared different Vpr-chloramphenicol acetyltransferase (CAT) fusion proteins for their virion incorporation ability and their effect on the infectivity of HIV viruses. Our deletion analysis indicates that both the N-terminal alpha-helical domain and the leucine/isoleucine-rich (LR) domain located in the middle region of Vpr are required for optimal virion incorporation of Vpr-CAT fusion proteins. The C-terminal basic region, associated with Vpr's ability to mediate cell cycle arrest in G2, was not required for virion incorporation, thus allowing the development of Vpr-based chimeric proteins devoid of any effect on cell growth. The fusion of Vpr at the N- or C-terminus of CAT targeted with equal efficiency the chimeric protein into virions. While the virion incorporation of most Vpr-CAT fusion proteins tested in this study was dependent on the presence of an intact p6 domain, fusion proteins containing only the N-terminal alpha-helical domain of Vpr (amino acid 1 to 42) were incorporated into virions in a p6-independent manner. Virion incorporation of Vpr-CAT fusion proteins was shown to decrease viral infectivity. Moreover, the insertion of HIV protease-cleavage sites between Vpr and CAT not only efficiently delivered and released the cleaved CAT product into HIV viral particles, but also greatly potentiated the inhibition of progeny virion infectivity. Overall, our study: (1) defines the Vpr sequence requirement and configuration necessary for the specific and optimal incorporation of Vpr fusion protein into HIV particles; (2) shows that Vpr fusion proteins have the ability to suppress HIV infectivity by targeting multiple steps of viral morphogenesis.
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PMID:HIV-1 Vpr-chloramphenicol acetyltransferase fusion proteins: sequence requirement for virion incorporation and analysis of antiviral effect. 1049 Jul 69

Homo- and hetero-oligomeric interactions between the transmembrane (TM) helices of integrin alpha and beta subunits may play an important role in integrin activation and clustering. As a first step to understanding these interactions, we used the TOXCAT assay to measure oligomerization of the wild-type alpha(IIb) TM helix and single-site TM domain mutants. TOXCAT measures the oligomerization of a chimeric protein containing a TM helix in the Escherichia coli inner membrane via the transcriptional activation of the gene for chloramphenicol acetyltransferase. We found the amount of chloramphenicol acetyltransferase induced by the wild-type alpha(IIb) TM helix was approximately half that induced by the strongly dimerizing TM helix of glycophorin A, confirming that the alpha(IIb) TM domain oligomerizes in biological membranes. Mutating each of the alpha(IIb) TM domain residues to either Ala, Leu, Ile, or Val revealed that a GXXXG motif mediates oligomerization. Further, we found that the residue preceding each glycine contributed to the oligomerization interface, as did the residue at position i + 4 after the second Gly of GXXXG. Thus, the sequence XXVGXXGGXXXLXX is critical for oligomerization of alpha(IIb) TM helix. These data were used to generate an atomic model of the alpha(IIb) homodimer, revealing a family of structures with right-handed crossing angles of 40 degrees to 60 degrees, consistent with a 4.0-residue periodicity, and with an interface rotated by 50 degrees relative to glycophorin A. Thus, although the alpha(IIb) TM helix makes use of the GXXXG framework, neighboring residues have evolved to engineer its dimerization interface, enabling it to subserve specific and specialized functions.
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PMID:Dimerization of the transmembrane domain of Integrin alphaIIb subunit in cell membranes. 1506 9


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