Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

By using whole-cell labeling assay with 125I-penicillin V, we observed a reduction in the binding of the radiolabeled beta-lactam to four or five penicillin-binding proteins (PBPs) in Haemophilus influenzae cells cultivated under specific conditions. PBPs 3A, 3B, 4, and 6 were altered after the growth of bacteria in diffusion chambers implanted in the peritoneal cavity of rats. PBP 2 was also modified when cells were cultivated in human cerebrospinal fluids. Because this observation may have important consequences on the efficacy of beta-lactams during antibiotic therapy, we characterized the physiological state of bacteria cultivated in animals in the hope of explaining how such important changes in cell properties develop in vivo. Since the development of natural genetic competence occurs at the stationary phase of growth in H. influenzae, we used a DNA transformation assay to evaluate the physiological state of bacteria grown in diffusion chambers implanted in rats. Chromosomal DNA isolated from an antibiotic-resistant donor strain was mixed with bacteria in diffusion chambers. At different times during a 5-h incubation period, recipient bacteria were collected from the chambers, CFU were determined by plate counting, and antibiotic-resistant transformants were isolated on selective plates. Genetic competence rapidly developed in cells grown in rats, and the frequency of transformation by test DNA was elevated. Electron microscopy revealed an irregular cell shape and blebs at the surface of bacteria cultivated in animals and in cerebrospinal fluids. In an attempt to induce a similar physiological state in vitro, we supplemented broth cultures with cyclic AMP or synchronized cultures by a nutritional upshift. No changes in PBPs were observed with supplemental cyclic AMP or during a single cell cycle. Finally, a reduction in the affinity of PBPs for 125I-penicillin V identical to that observed in bacteria grown in rats was observed in cells isolated from the stationary phase of growth in vitro. These results clearly indicate that H. influenzae cells grown in animals undergo a rapid change to a physiological state similar to that found in late-stationary-phase cultures in vitro. This observation indicates that the rational design of future and improved antibiotic therapy of H. influenzae infections should consider cell properties of slow-growing or latent bacteria.
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PMID:Modification in penicillin-binding proteins during in vivo development of genetic competence of Haemophilus influenzae is associated with a rapid change in the physiological state of cells. 132 54

A plasmid library of PstI fragments of Haemophilus influenzae Rd genomic DNA was mutagenized in Escherichia coli with mini-Tn10kan. The mutagenized PstI fragments were introduced by transformation into the H. influenzae chromosome, and kanamycin-resistant transformants were screened for the transformation-deficient phenotype by a cyclic AMP-DNA plate method. Fifty-four mutant strains containing 24 unique insertions that mapped to 10 different PstI fragments were isolated. Strains carrying unique insertions were tested individually for DNA uptake, transformation efficiency, UV sensitivity, and growth rate. The transformation frequencies of these mutants were decreased by factors of 10(-2) to 10(-6). Five of the mutants had normal competence-induced DNA uptake, and the rest were variably deficient in competence development. Three strains were moderately UV sensitive. All strains but one had doubling times within 50% of that of the wild type. Mutated genes were cloned into an H. influenzae-E. coli shuttle vector, and wild-type loci were recovered by in vivo recombinational exchange. Hybridization of these clones to SmaI genomic fragments separated in pulsed-field gels showed that these insertions were not clustered in a particular region of the chromosome.
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PMID:Transposon mutagenesis, characterization, and cloning of transformation genes of Haemophilus influenzae Rd. 254 55

The 2':3'-cyclic nucleotide phosphodiesterase:3'-nucleotidase of Haemophilus influenzae was purified from a periplasmic preparation by affinity chromatographic techniques. The enzyme-catalysed hydrolysis of 2':3'-cyclic AMP to adenosine without accumulation of the intermediate substrate 3'-AMP was demonstrated by high performance liquid chromatography. Competitive inhibition of the enzyme by a variety of nucleosides and mononucleotides indicated the presence of either purine or pyrimidine bases to be essential for selective interactions with the enzyme, and confirmed the need for a 3'-position phosphate for the functioning of mononucleotides as substrates for the enzyme. The enzyme had a molecular weight of 79 000, was stable at low temperatures and was thermally denatured at temperatures above 50 degrees C.
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PMID:Studies of the 2':3'-cyclic nucleotide phosphodiesterase of Haemophilus influenzae. 299 67

A nucleotide pyrophosphatase isolated from Haemophilus influenzae was purified to electrophoretic homogeneity and characterized with respect to molecular weight, substrate specificity, pH profile, thermal stability, functional group involvement, and effectiveness of selective inhibition. The enzyme catalyzes the hydrolysis of NAD to NMN and AMP and appears located appropriately to facilitate the internalization of NAD needed to satisfy the V-factor growth requirement of the organism. In the processing of NAD and structurally related substrates, the enzyme exhibited negative cooperativity. Structural alterations in the purine moiety of these dinucleotide substrates had pronounced effects on the negative cooperativity of the enzyme. AMP, ADP, and several related nucleotides were observed to be effective substrate-competitive inhibitors of the enzyme. Several of the dinucleotides serving as substrates for the nucleotide pyrophosphatase were evaluated with respect to substituting for NAD in supporting growth of the organism. AMP and ADP inhibited growth of the organism when NAD served as V-factor, and this inhibition correlated well with the inhibitory effects of these nucleotides on the purified nucleotide pyrophosphatase.
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PMID:Characterization of Haemophilus influenzae nucleotide pyrophosphatase. An enzyme of critical importance for growth of the organism. 300 42

A new reagent for the detection of penicillin-binding proteins (PBPs) was developed. An N-hydroxysuccinimide ester of biotin was used to tag beta-lactam antibiotics with free side chain amino groups such as ampicillin (BIO-AMP), 6-aminopenicillanic acid (BIO-APA), and 7-aminocephalosporanic acid (BIO-ACA). Bacterial PBPs from cells or isolated cytoplasmic membranes of Escherichia coli, Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pneumoniae were labeled with BIO-AMP, subjected to electrophoresis on sodium dodecyl sulfate (SDS)-polyacrylamide gels, and transferred onto nitrocellulose membranes. Electrophoretic PBP profiles were detected on blots, using colorimetric or chemiluminescence systems, on the basis of the interaction of BIO-AMP-PBP complexes and a streptavidin-peroxidase conjugate. The chemiluminescent reaction permitted a high sensitivity of detection, and PBP profiles could be determined within seconds. All PBP profiles were similar to those obtained with a traditional PBP labeling technique with 125I-labeled penicillin V, except that an additional unidentified PBP (approximately 55,000 Da) was labeled with BIO-AMP in E. coli and H. influenzae. Differences in the intensities of labeling for specific PBPs were observed between the chemiluminescent and radioactive labeling agents and were attributed to the differences in their affinities for PBPs. Similarly, BIO-AMP, BIO-APA, and BIO-ACA produced different PBP profiles. We also investigated the use of BIO-AMP in PBP purification. BIO-AMP-PBP complexes from a mixture of H. influenzae proteins were allowed to bind to avidin immobilized on an agarose support in a microcentrifuge tube. After several washes in the presence of salts, PBPs were eluted by boiling and treatment with SDS. The eluted proteins were separated by electrophoresis on SDS-polyacrylamide gels, and biotinylated proteins were identified on blots by a chemiluminescence reaction. Biotinylation of beta-lactams is rapid, safe, and inexpensive. Our results demonstrate the feasibility of using biotinylated beta-lactams as nonradioactive reagents for the study of PBPs and for the purification of these proteins.
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PMID:Use of biotinylated beta-lactams and chemiluminescence for study and purification of penicillin-binding proteins in bacteria. 806 79

Competence for transformation in Haemophilus influenzae is stimulated by cyclic AMP (cAMP) and requires the cAMP-dependent catabolite regulatory protein CRP. Thus, understanding the control of competence will require understanding how cAMP levels are regulated. As a first step, we have cloned the H. influenzae adenylate cyclase gene (cya) by complementing the Lac- phenotype of delta cya Escherichia coli. Its sequence specifies an 843-amino-acid protein which has significant identity to other known bacterial adenylate cyclases (41 to 43% and 61% identical to the cya genes of enteric bacteria and of Pasteurella multocida, respectively). As seen in other bacterial cya genes, there is evidence for regulation similar to that demonstrated for E. coli: the presence of a strong consensus CRP binding site within the promoter of the gene may provide feedback control of cAMP levels by repressing cya transcription, and translation may be limited by the weak ribosome binding site and by initiation of protein synthesis with GUG rather than AUG or the UUG used in other bacterial cya genes. We confirmed the essential role of cAMP in competence by constructing and characterizing H. influenzae cya mutants. This strain failed to develop competence either spontaneously or after transfer to a competence-inducing medium. However, it became as competent as its wild-type parent in the presence of exogenous cAMP. This result suggests that the failure of exogenously added cAMP to induce optimum competence in wild-type cells is not due to a limitation to the entry of cAMP into the cells. Rather, it strongly favors models in which competence induction requires both an increase in intracellular cAMP and a second as yet unidentified regulatory event. H. influenzae strains mutant in cya or crp were unable to ferment xylose or ribose. This confirms that influenzae, like E. coli, uses cAMP and CRP to regulate nutrient uptake and utilization and lends increasing support to the hypothesis that DNA uptake is mechanism of nutrient acquisition.
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PMID:The Haemophilus influenzae adenylate cyclase gene: cloning, sequence, and essential role in competence. 822 61

The Haemophilus influenzae rec-1+ protein plays a central role in DNA metabolism, participating in general homologous recombination, recombinational (postreplication) DNA repair, and prophage induction. Although many H. influenzae rec-1 mutants have been phenotypically characterized, little is known about the rec-1+ gene at the molecular level. In this study, we present the genetic organization of the rec-1+ locus, the DNA sequence of rec-1+, and studies of the transcriptional regulation of rec-1+ during cellular assault by DNA-damaging agents and during the induction of competence for genetic transformation. Although little is known about promoter structure in H. influenzae, we identified a potential rec-1+ promoter that is identical in 11 of 12 positions to the bacterial sigma 70-dependent promoter consensus sequence. Results from a primer extension analysis revealed that the start site of rec-1+ transcription is centered 6 nucleotides downstream of this promoter. We identified potential DNA binding sites in the rec-1+ gene for LexA, integration host factor, and cyclic AMP receptor protein. We obtained evidence that at least one of the proposed cyclic AMP receptor protein binding sites is active in modulating rec-1+ transcription. This finding makes rec-1+ control circuitry novel among recA+ homologs. Two H. influenzae DNA uptake sequences that may function as a transcription termination signal were identified in inverted orientations at the end of the rec-1+ coding sequence. In addition, we report the first use of the Escherichia coli lacZ operon fusion technique in H. influenzae to study the transcriptional control of rec-1+. Our results indicate that rec-1+ is transcriptionally induced about threefold during DNA-damaging events. Furthermore, we show that rec-1+ can substitute for recA+ in E. coli to modulate SOS induction of dinB1 expression. Surprisingly, although 5% of the H. influenzae genome is in the form of single-stranded DNA during competence for genetic transformation, an event that could be a potent SOS-inducing signal, we failed to detect significant changes in rec-1+ transcription during the induction of genetic competence.
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PMID:Structural organization, nucleotide sequence, and regulation of the Haemophilus influenzae rec-1+ gene. 822 74

A 0.972-kilobase pair DNA fragment from Streptomyces lividans that induces the production of the blue-pigmented antibiotic actinorhodine in S. lividans when cloned on a multicopy plasmid has led to the isolation of a 4-kilobase pair DNA fragment from Streptomyces coelicolor containing homologous sequence. Computer-assisted analysis of the DNA sequence revealed three putative open reading frames (ORFs), ORF1, ORF2, and ORF3. ORF2 extends beyond the sequenced DNA fragment, and its deduced product shares no similarities with any other known proteins in the data bases. ORF3 is also truncated, and its 41-amino acid C-terminal product is identical to the S. coelicolor adenine phosphoribosyltransferase. The 847-amino acid ORF1 protein, with a predicted molecular mass of 94.2 kDa, strongly resembled the relA and spoT gene products from Escherichia coli and the homologs from Vibrio sp. strain S14, Haemophilus influenzae, Streptococcus equisimilis H46A, and Mycoplasma genitalium. Unlike these proteins, the ORF1 amino acid sequence analysis revealed the presence of a putative ATP/GTP-binding domain. A mutant was generated by deleting most of the ORF1 gene that showed an actinorhodine-nonproducing phenotype, while undecylprodigiosin and the calcium-dependent antibiotic were unaffected. The mutant strain grew at a much lower rate than the wild-type strain, and spore formation was delayed. When the gene was propagated on a low copy number vector, not only was actinorhodine production restored, but actinorhodine and undecylprodigiosin production was enhanced in both the mutant and wild-type and morphological differentiation returned to wild-type characteristics. (p)ppGpp synthetase activity was not detected in purified ribosomes from the ORF1-deleted mutant, while it was restored by complementation of this strain.
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PMID:A relA/spoT homologous gene from Streptomyces coelicolor A3(2) controls antibiotic biosynthetic genes. 863 67

Haemophilus influenzae Rd becomes competent for transformation by nutritional downshift or transient anaerobic growth through a process that requires cyclic AMP receptor protein and adenylate cyclase. Insertion mutations in crr or ptsI of the phosphoenolpyruvate:carbohydrate phosphotransferase system lowered transformation frequencies, and the effect was reversed by the addition of cyclic AMP. However, insertions into H. influenzae homologs of two-component signal transduction genes had no effect on competence.
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PMID:Role of the two-component signal transduction and the phosphoenolpyruvate: carbohydrate phosphotransferase systems in competence development of Haemophilus influenzae Rd. 889 43

Haemophilus influenzae Rd is a gram-negative bacterium capable of natural DNA transformation. The competent state occurs naturally in late exponential growth or can be induced by a nutritional downshift or by transient anaerobiosis. The genes cya, crp, topA, and sxy (tfoX) are known to function in the regulation of competence development. The phosphoenolpyruvate:carbohydrate phosphotransferase system functions to maintain levels of cyclic AMP necessary for competence development but is not directly involved in regulation. The exact signal(s) for competence and the genes that mediate the signal(s) are still unknown. In an effort to find additional regulatory genes, H. influenzae Rd was mutated by using an in vitro Tn7 system and screened for mutants with a reduced ability to induce the competence-regulatory gene, comA. Insertions in atpA, a gene coding for the alpha subunit of the F1 cytoplasmic domain of the ATP synthase, reduce transformation frequencies about 20-fold and cause a significant reduction in expression of competence-regulatory genes, while the expression of constitutive competence genes is only minimally affected. In addition, we found that an insertion in atpB, which encodes the a subunit of the F0 membrane-spanning domain, has a similar effect on transformation frequencies.
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PMID:In vitro Tn7 mutagenesis of Haemophilus influenzae Rd and characterization of the role of atpA in transformation. 939 95


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