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)

Chlamydia trachomatis is a nucleotide parasite, being entirely dependent on its host eukaryotic cell for a supply of ATP, GTP, and UTP. Chlamydiae are not, however, auxotrophic for CTP, as they are able both to transport CTP from the host and synthesize CTP de novo via a chlamydial CTP synthetase. This study addresses the developmental regulation of CTP synthetase over the course of the C. trachomatis life cycle. Given the distinct life stages of C. trachomatis, analysis of temporal changes in gene expression and regulation of protein activity is the key to unravelling the mechanism of pathogenesis of this bacterium. The results of immunodetection analysis indicate that CTP synthetase is present in C. trachomatis elementary bodies and reticulate bodies and that it is widespread in other chlamydial strains. Reverse transcriptase-polymerase chain reaction (RT-PCR) and metabolic labelling experiments show that CTP synthetase is transcribed and translated primarily during the mid- and late stages of the chlamydial growth cycle. In addition, C. trachomatis CTP synthetase was transcribed with the CTP utilizing enzyme CMP-2-keto-3-deoxy-octanoic acid synthetase (CMP-KDO synthetase) as part of a polycistronic mRNA. The co-expression of these two enzymes suggests a role for CTP synthetase in lipopolysaccharide biosynthesis, potentially channelling CTP directly to CMP-KDO synthetase. The ability of the intact operon to complement CTP synthetase and CMP-KDO deficiencies in mutant Escherichia coli strains indicates that both enzymes are efficiently translated from a single messenger RNA. Kinetic analysis revealed that the C. trachomatis CTP synthetase possessed co-operativity patterns typical of both prokaryotic and eukaryotic CTP synthetases. However, the K(m) of the enzyme for UTP was lower than that of E. coli CTP synthetase, presumably in response to the low intracellular concentration of this nucleotide in C. trachomatis.
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PMID:Chlamydia trachomatis CTP synthetase: molecular characterization and developmental regulation of expression. 895 11

Chlamydiae are obligate intracellular bacteria that replicate within a non-acidified vacuole, termed an inclusion. To identify chlamydial proteins that are unique to the intracellular phase of the life cycle, a lambda expression library of Chlamydia psittaci DNA was differentially screened with convalescent antisera from infected guinea pigs and antisera directed at formalin-fixed purified chlamydial elementary bodies (EBs). One library clone was identified that harboured two open reading frames (ORFs) with coding potential for similar-sized proteins of approximately 20 kDa. These proteins were subsequently termed IncB and IncC. Sequencing of the cloned insert revealed a strong Escherichia coli-like promoter sequence immediately upstream of incB and a 36nt intergenic region between the ORFs. Sequence analysis of the region upstream of incB and incC revealed two ORFs that had strong homologies to an amino acid transporter and a sodium-dependent transporter. Immunoblotting with antisera directed at IncB or IncC demonstrated that these proteins are present in C. psittaci-infected HeLa cells but are absent or below the level of detection in purified EBs. Reverse transcriptase-polymerase chain reactions provided evidence that incB and incC are transcribed in an operon. Immunofluorescence microscopy demonstrated that IncB and IncC are each localized to the inclusion membrane of infected cells. No primary sequence similarity is evident between IncA, IncB or IncC, but each contains a large hydrophobic domain of similar size and character as in IncA. Analysis of the recently completed C. trachomatis serovar D genome database has revealed C. trachomatis ORFs encoding homologues to incB and incC, indicating that these genes are conserved among the chlamydiae.
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PMID:Tandem genes of Chlamydia psittaci that encode proteins localized to the inclusion membrane. 966 87

Chlamydia trachomatis is a bacterial obligate intracellular parasite that replicates within a vacuole, termed an inclusion, that does not fuse with lysosomes. Within 2 h after internalization, the C. trachomatis inclusion ceases to interact with the endocytic pathway and, instead, becomes fusogenic with exocytic vesicles containing exogenously synthesized NBD-sphingomyelin. Both fusion of exocytic vesicles and long-term avoidance of lysosomal fusion require early chlamydial gene expression. Modification of the chlamydial inclusion probably occurs through the expression and insertion of chlamydial protein(s) into the inclusion membrane. To identify candidate inclusion membrane proteins, antisera were raised against a total membrane fraction purified from C. trachomatis-infected HeLa cells. By indirect immunofluorescence, this antisera recognized the inclusion membrane and, by immunoblot analysis, recognized three chlamydial-specific antigens of approximate molecular weights 15, 18 and 21 kDa. IncG, encoding an 18 kDa and 21 kDa doublet chlamydial antigen, was identified by screening a C. trachomatis, serovar L2, genomic expression library. Three additional genes, incD, incE and incF, were co-transcribed with incG. Monospecific antisera against each of the four genes of this operon demonstrated that the gene products were localized to the chlamydial inclusion membrane. Immediately downstream from the operon containing incD-G was the C. trachomatis homologue of incA. Like IncD, E, F and G, C. trachomatis IncA is also localized to the inclusion membrane. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated that IncD-G, but not incA, are transcribed within the first 2 h after internalization, making them candidates for chlamydial factors required for the modification of the nascent chlamydial inclusion.
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PMID:Identification and characterization of a Chlamydia trachomatis early operon encoding four novel inclusion membrane proteins. 1044 85

The biological significance of glycogen accumulation and how the process is regulated in Chlamydia trachomatis remains poorly defined. C. trachomatis-infected HeLa cells were cultured in medium containing various glucose concentrations (0, 0.1, 1 or 10 mg ml-1) or in the presence of gluconeogenic carbon sources (20 mM glutamate, 20 mM malate, 20 mM alpha-ketoglutarate or 20 mM oxaloacetate), and the effects of these different culture conditions on the production of infectious chlamydial elementary bodies and glycogen accumulation were monitored. When chlamydiae were cultured in glucose concentrations greater than 1 mg ml-1, optimal growth and maximal glycogen accumulation occurred. In contrast to uninfected HeLa cells, which increased their glycogen stores when grown in the presence of high glucose concentrations, chlamydial glycogen accumulation remained essentially constant. When cultured in medium supplemented with either reduced glucose concentrations or any of the gluconeogenic carbon sources, chlamydiae still grew; however, the yield of elementary bodies was substantially decreased, and there was no significant amount of glycogen accumulated by host HeLa cells or C. trachomatis. This suggests that glycogen accumulation may not be essential for chlamydial survival. Reverse transcriptase-polymerase chain reaction (RT-PCR) results indicated that, despite the fact that the source and amount of carbon available in the medium affected chlamydial glycogen accumulation, the expression of genes required for glycogen metabolism was not significantly changed. Similarly, the expression of several genes encoding key enzymes of central metabolism was not affected by alterations in carbon source or availability. Taken together, the data suggest that, unlike most free-living bacteria, chlamydia are unable to alter the expression of genes involved in carbon metabolism in response to changes in environmental conditions.
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PMID:Regulation of carbon metabolism in Chlamydia trachomatis. 1102 87

The genome of the obligate intracellular bacterium Chlamydia pneumoniae CWL029 encodes a family of 21 proteins with predicted outer membrane localization. These polymorphic membrane proteins (Pmps) are heterogeneous in both amino acid sequence and predicted size but are unified by the conserved amino acid motifs GGAI and FXXN repeated in the N-terminal half of each protein. Reverse transcriptase PCR analysis showed that all pmp genes are transcribed. To determine whether all proteins are expressed, specific antisera were generated by immunization with mutually exclusive synthetic peptides representing each of the 21 predicted Pmps. Each antiserum reacted with, and was typically immunospecific for, the corresponding peptide immunogen by enzyme-linked immunosorbent assay. Western blot analyses of purified elementary bodies showed that 11 of the 21 Pmps were detectable. Attempts to demonstrate by Sarykosyl fractionation that the Pmps were localized to the outer membrane revealed that several of the Pmps were unstable and readily degraded. Analyses of additional C. pneumoniae strains showed that although some Pmps are conserved, others vary between strains, in both molecular weight and level of expression.
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PMID:Expression of Chlamydia pneumoniae polymorphic membrane protein family genes. 1125 97

Smooth muscle cell (SMC) proliferation and intimal thickening are hallmark features of atherosclerotic disease, and Chlamydia pneumoniae may contribute to atherogenesis by imparting biological effects on SMCs. An in vitro endothelial cell model and a normocholesterolemic rabbit model were used to test the hypothesis that infection with C. pneumoniae induces SMC growth factor production, SMC proliferation, and aortic intimal thickening. Using reverse-transcriptase polymerase chain reaction, it was demonstrated that C. pneumoniae infection of endothelial cells induced platelet-derived growth factor (PDGF)-B messenger RNA expression. In C. pneumoniae-infected rabbits, maximum intimal thickness (MIT) was significantly greater than that in uninfected animals (P< .0001). MIT correlated with the presence of C. pneumoniae antigen (P= .043) and PDGF-B (P= .002) in aortic tissues, and C. pneumoniae antigen was independently correlated with the presence of PDGF-B in aortic tissues (P= .009). These results suggest that C. pneumoniae-induced SMC proliferation and intimal thickening may be mediated through PDGF-B and may be a molecular mechanism by which C. pneumoniae infection could contribute to atherogenesis.
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PMID:Chlamydia pneumoniae infection of endothelial cells induces transcriptional activation of platelet-derived growth factor-B: a potential link to intimal thickening in a rabbit model of atherosclerosis. 1202 68

Chlamydia trachomatis is an obligate intracellular bacterium that develops within a parasitophorous vacuole termed an inclusion. The inclusion is nonfusogenic with lysosomes but intercepts lipids from a host cell exocytic pathway. Initiation of chlamydial development is concurrent with modification of the inclusion membrane by a set of C. trachomatis-encoded proteins collectively designated Incs. One of these Incs, IncA, is functionally associated with the homotypic fusion of inclusions. Inclusions also do not fuse when cultures are multiply infected with C. trachomatis and cultivated at 32 degrees C. We obtained evidence linking these experimental observations by characterizing IncA localization in 32 degrees C cultures. Analysis of inclusions by light and transmission electron microscopy confirmed that HeLa cells infected with multiple C. trachomatis elementary bodies and cultivated at 32 degrees C for 24 h contained multiple, independent inclusions. Reverse transcriptase PCR and immunoblot analyses of C. trachomatis-infected HeLa cells demonstrated the presence of IncA at 24 h in 32 degrees C cultures. When parallel cultures were probed with IncA-specific antibodies in indirect immunofluorescence assays, IncA was detectable in intracellular chlamydiae but not within the inclusion membrane. In addition, analysis of purified reticulate bodies from 37 and 32 degrees C cultures showed that bacterium-associated pools of IncA are enriched in cultures grown at 32 degrees C. Microscopic observation of infected cells revealed that some vacuoles had fused by 48 h postinfection, and this finding was correlated with the detection of IncA in inclusion membranes by immunofluorescence microscopy. The data are consistent with a requirement for IncA in fusions of C. trachomatis inclusions and suggest that the effect of incubation at 32 degrees C is manifested by restricted export of IncA to the inclusion membrane.
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PMID:Inhibition of fusion of Chlamydia trachomatis inclusions at 32 degrees C correlates with restricted export of IncA. 1206 25

Co-infection has been reported in patients with severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, but there is limited knowledge on co-infection among patients with coronavirus disease 2019 (COVID-19). The prevalence of co-infection was variable among COVID-19 patients in different studies, however, it could be up to 50% among non-survivors. Co-pathogens included bacteria, such as Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumonia, Legionella pneumophila and Acinetobacter baumannii; Candida species and Aspergillus flavus; and viruses such as influenza, coronavirus, rhinovirus/enterovirus, parainfluenza, metapneumovirus, influenza B virus, and human immunodeficiency virus. Influenza A was one of the most common co-infective viruses, which may have caused initial false-negative results of real-time reverse-transcriptase polymerase chain reaction for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Laboratory and imaging findings alone cannot help distinguish co-infection from SARS-CoV-2 infection. Newly developed syndromic multiplex panels that incorporate SARS-CoV-2 may facilitate the early detection of co-infection among COVID-19 patients. By contrast, clinicians cannot rule out SARS-CoV-2 infection by ruling in other respiratory pathogens through old syndromic multiplex panels at this stage of the COVID-19 pandemic. Therefore, clinicians must have a high index of suspicion for coinfection among COVID-19 patients. Clinicians can neither rule out other co-infections caused by respiratory pathogens by diagnosing SARS-CoV-2 infection nor rule out COVID-19 by detection of non-SARS-CoV-2 respiratory pathogens. After recognizing the possible pathogens causing co-infection among COVID-19 patients, appropriate antimicrobial agents can be recommended.
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PMID:Co-infections among patients with COVID-19: The need for combination therapy with non-anti-SARS-CoV-2 agents? 3248 66

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