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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study, we identified and characterized a novel secreted protein, the extracellular serine protease EspP, which is encoded by the large plasmid of enterohaemorrhagic Escherichia coli (EHEC) O157:H7. The corresponding espP gene consists of a 3900 bp open reading frame that is able to encode a 1300-amino-acid protein. EspP is synthesized as a large precursor which is then processed at the N- and C-termini during secretion. It can be grouped into the autotransporter protein family. The deduced amino acid sequence of EspP showed homology to several secreted or surface-exposed proteins of pathogenic bacteria, in particular EspC of enteropathogenic E. coli and IgA1 proteases from Neisseria spp. and Haemophilus influenzae. Hybridization experiments and immunoblot analysis of clinical EHEC isolates showed that EspP is widespread among EHEC of the serogroup O157 and that it also exists in serogroup 026. A specific immune response against EspP was detected in sera from patients suffering from EHEC infections. Functional analysis showed that EspP is a protease capable of cleaving pepsin A and human coagulation factor V. Degradation of factor V could contribute to the mucosal haemorrhage observed in patients with haemorrhagic colitis.
Mol Microbiol 1997 May
PMID:EspP, a novel extracellular serine protease of enterohaemorrhagic Escherichia coli O157:H7 cleaves human coagulation factor V. 919 4

This study describes the characterization of BpH3, a Bordetella pertussis DNA-binding protein. Sequence analysis reveals significant homology with the H-NS sequence of Escherichia coli and Haemophilus influenzae, particularly in the C-terminal part of the proteins. Our results provide evidence that H-NS and BpH3 display functional homology. First, expression of BpH3 in an hns mutant results in restoration of motility, an H-NS-dependent phenotype. This effect is dependent on the level of BpH3 expression and results from transcriptional activation of the flagellar master operon. Second, the high level of beta-glucosidase associated with hns mutations is reversed to the low wild-type level in the presence of BpH3. Third, BpH3 is able, like H-NS, to preferentially bind in vitro to curved DNA fragments, such as flhDC and bla promoter regions. Our results are the first demonstration that proteins homologous to H-NS exist in bacteria phylogenetically distant from H. influenzae and enterobacteria.
Mol Microbiol 1997 May
PMID:Characterization of BpH3, an H-NS-like protein in Bordetella pertussis. 919 8

The use of primers synthesized to eight class II restriction endonuclease target sequences, from Haemophilus parainfluenzae, Escherichia coli, Staphylococcus aureus, Salmonella infantis, Rhodobacter sphaeroides, Klebsiella pneumoniae, Bacillus amyloliquefaciens and Proteus vulgaris for single and multiplex PCR identification of the organisms is discussed. Results indicate that the method is sensitive and specific enough to detect single cells and attogram amounts of target DNA. It has also been demonstrated that the primers can be used in whole cell PCR for identification and whole cell PCR product recovery could be enhanced by the addition of gelatin or DMSO to PCR reaction mixtures. Other results have indicated that the method can be used for the definite identification of specific individuals present in mixed cultures or suspensions of organisms. The applicability of the method for detection of a specific strain within a group of closely related organisms has also been investigated and for that sequence/organism the results suggest that the proposed method is indeed very specific and discriminative. It is suggested that as more information becomes available regarding such sequences and their distribution, this approach could form the basis of a widescale, rapid, simple and cheap identification and/or typing system for bacteria.
Mol Cell Probes 1997 Aug
PMID:Rapid, sensitive, microbial detection by gene amplification using restriction endonuclease target sequences. 928 17

The genomes of three bacteria (Haemophilus influenzae, Mycoplasma genitalium, and Escherichia coli) and two eukaryotes (Saccharomyces cerevisiae and Caenorhabditis elegans) were compared. The distribution of their putative open reading frames (ORFs) was studied, and several conclusions were drawn: (1) All of these genomes, even the smallest, exhibit a significant proportion (7%-30%) of duplicated ORFs. This proportion is a function of genome size and appears unrelated to the bacteria/eukaryote division. (2) Some of these ORFs constitute families of up 20 or more members. (3) The levels of sequence similarity within these families are highly variable and their distribution is different among bacteria and eukaryotes. (4) In yeast, there are topological relationships between members of the same family. The paired ORFs are frequently in the same orientation with regard to their respective telomeres and located at comparable distances from them.
Mol Biol Evol 1997 Oct
PMID:A comparative study of duplications in bacteria and eukaryotes: the importance of telomeres. 933 46

Five complete bacterial genome sequences have been released to the scientific community. These include four (eu)Bacteria, Haemophilus influenzae, Mycoplasma genitalium, M. pneumoniae, and Synechocystis PCC 6803, as well as one Archaeon, Methanococcus jannaschii. Features of organization shared by these genomes are likely to have arisen very early in the history of the bacteria and thus can be expected to provide further insight into the nature of early ancestors. Results of a genome comparison of these five organisms confirm earlier observations that gene order is remarkably unpreserved. There are, nevertheless, at least 16 clusters of two or more genes whose order remains the same among the four (eu)Bacteria and these are presumed to reflect conserved elements of coordinated gene expression that require gene proximity. Eight of these gene orders are essentially conserved in the Archaea as well. Many of these clusters are known to be regulated by RNA-level mechanisms in Escherichia coli, which supports the earlier suggestion that this type of regulation of gene expression may have arisen very early. We conclude that although the last common ancestor may have had a DNA genome, it likely was preceded by progenotes with an RNA genome.
J Mol Evol 1997 Nov
PMID:Conserved gene clusters in bacterial genomes provide further support for the primacy of RNA. 934 94

Ferric-binding proteins (FbpA) have been implicated in the transferrin receptor-mediated iron acquisition pathways of Haemophilus influenzae and Neisseria spp. These proteins are believed to function by shuttling iron from outer membrane transferrin receptors to a specific inner membrane permease complex. However, the role of these proteins has not been conclusively resolved, as attempts at creating isogenic mutants in the fbpA genes of both species have been unsuccessful, prompting the hypothesis that FbpA may play a critical role in H. influenzae and Neisseria spp. This study describes the construction and characterization of an H. influenzae isogenic fbpA mutant. It is demonstrated that this mutant is deficient in its ability to use human transferrin as a sole iron source, even though the strain is still competent for binding human transferrin. It is also demonstrated that this mutant is impaired in its ability to use ferric citrate as an iron source, and grows at a reduced rate relative to wild type in broth supplemented with protoporphyrin rather than haemin.
Mol Microbiol 1997 Sep
PMID:Characterization of a ferric-binding protein mutant in Haemophilus influenzae. 936 22

Protein sequences encoded in three complete bacterial genomes, those of Haemophilus influenzae, Mycoplasma genitalium and Synechocystis sp., and the first available archaeal genome sequence, that of Methanococcus jannaschii, were analysed using the BLAST2 algorithm and methods for amino acid motif detection. Between 75% and 90% of the predicted proteins encoded in each of the bacterial genomes and 73% of the M. jannaschii proteins showed significant sequence similarity to proteins from other species. The fraction of bacterial and archaeal proteins containing regions conserved over long phylogenetic distances is nearly the same and close to 70%. Functions of 70-85% of the bacterial proteins and about 70% of the archaeal proteins were predicted with varying precision. This contrasts with the previous report that more than half of the archaeal proteins have no homologues and shows that, with more sensitive methods and detailed analysis of conserved motifs, archaeal genomes become as amenable to meaningful interpretation by computer as bacterial genomes. The analysis of conserved motifs resulted in the prediction of a number of previously undetected functions of bacterial and archaeal proteins and in the identification of novel protein families. In spite of the generally high conservation of protein sequences, orthologues of 25% or less of the M. jannaschii genes were detected in each individual completely sequenced genome, supporting the uniqueness of archaea as a distinct domain of life. About 53% of the M. jannaschii proteins belong to families of paralogues, a fraction similar to that in bacteria with larger genomes, such as Synechocystis sp. and Escherichia coli, but higher than that in H. influenzae, which has approximately the same number of genes as M. jannaschii. Certain groups of proteins, e.g. molecular chaperones and DNA repair enzymes, thought to be ubiquitous and represented in the minimal gene set derived by bacterial genome comparison, are missing in M. jannaschii, indicating massive non-orthologous displacement of genes responsible for essential functions. An unexpectedly large fraction of the M. jannaschii gene products, 44%, shows significantly higher similarity to bacterial than to eukaryotic proteins, compared with 13% that have eukaryotic proteins as their closest homologues (the rest of the proteins show approximately the same level of similarity to bacterial and eukaryotic homologues or have no homologues). Proteins involved in translation, transcription, replication and protein secretion are most closely related to eukaryotic proteins, whereas metabolic enzymes, metabolite uptake systems, enzymes for cell wall biosynthesis and many uncharacterized proteins appear to be 'bacterial'. A similar prevalence of proteins of apparent bacterial origin was observed among the currently available sequences from the distantly related archaeal genus, Sulfolobus. It is likely that the evolution of archaea included at least one major merger between ancestral cells from the bacterial lineage and the lineage leading to the eukaryotic nucleocytoplasm.
Mol Microbiol 1997 Aug
PMID:Comparison of archaeal and bacterial genomes: computer analysis of protein sequences predicts novel functions and suggests a chimeric origin for the archaea. 1074 90

To test the hypotheses that eubacterial genomes leave evolutionarily stable structures and that the variety of genome size is brought about through genome doubling during evolution, the genome structures of Haemophilus influenzae, Mycoplasma genitalium, Escherichia coli, and Bacillus subtilis were compared using the DNA sequences of the entire genome or substantial portions of genome. In these comparisons, the locations of orthologous genes were examined among different genomes. Using orthologous genes for the comparisons guaranteed that differences revealed in physical location would reflect changes in genome structure after speciation. We found that dynamic rearrangements have so frequently occurred in eubacterial genomes as to break operon structures during evolution, even after the relatively recent divergence between E. coli and H. influenzae. Interestingly, in such eubacterial genomes of high plasticity, we could find several highly conservative regions with the longest conserved region comprising the S10, spc, and alpha operons. This suggests that such exceptional conservative regions have undergone strong structural constraints during evolution.
J Mol Evol 1997
PMID:Genome plasticity as a paradigm of eubacteria evolution. 939 6

Haemophilus influenzae elaborates a surface protein called Hap, which is associated with the capacity for intimate interaction with cultured epithelial cells. Expression of hap results in the production of three protein species: outer membrane proteins of approximately 155 kDa and 45 kDa and an extracellular protein of approximately 110 kDa. The 155 kDa protein corresponds to full-length mature Hap (without the signal sequence), and the 110 kDa extracellular protein represents the N-terminal portion of mature Hap (designated Haps). In the present study, we examined the mechanism of processing and secretion of Hap. Site-directed mutagenesis suggested that Hap is a serine protease that undergoes autoproteolytic cleavage to generate the 110 kDa extracellular protein and the 45 kDa outer membrane protein. Biochemical analysis confirmed this conclusion and established that cleavage occurs on the bacterial cell surface. Determination of N-terminal amino acid sequence and mutagenesis studies revealed that the 45 kDa protein corresponds to the C-terminal portion of Hap, starting at N1037. Analysis of the secondary structure of this protein (designated Hap beta) predicted formation of a beta-barrel with an N-terminal transmembrane alpha-helix followed by 14 transmembrane beta-strands. Additional analysis revealed that the final beta-strand contains an amino acid motif common to other beta-barrel outer membrane proteins. Upon deletion of this entire C-terminal consensus motif, Hap could no longer be detected in the outer membrane, and secretion of Haps was abolished. Deletion or complete alteration of the final three amino acid residues had a similar but less dramatic effect, suggesting that this terminal tripeptide is particularly important for outer membrane localization and/or stability of the protein. In contrast, isolated point mutations that disrupted the amphipathic nature of the consensus motif or eliminated the C-terminal tryptophan had no effect on outer membrane localization of Hap or secretion of Haps. These results provide insight into a growing family of Gram-negative bacterial exoproteins that are secreted by an IgA1 protease-like mechanism; in addition, they contribute to a better understanding of the structural determinants of targeting of beta-barrel proteins to the bacterial outer membrane.
Mol Microbiol 1997 Nov
PMID:Structural determinants of processing and secretion of the Haemophilus influenzae hap protein. 940 21

Representative genomes from each of the three kingdoms of life are compared in terms of protein structure, in particular, those of Haemophilus influenzae (a bacteria), Methanococcus jannaschii (an archaeon), and yeast (a eukaryote). The comparison is in the form of a census (or comprehensive accounting) of the relative occurrence of secondary and tertiary structures in the genomes, which particular emphasis on patterns of supersecondary structure. Comparison of secondary structure shows that the three genomes have nearly the same overall secondary-structure content, although they differ markedly in amino acid composition. Comparison of super-secondary structure, using a novel "frequent-words" approach, shows that yeast has a preponderance of consecutive strands (e.g. beta-beta-beta patterns), Haemophilus, consecutive helices (alpha-alpha-alpha), and Methanococcus, alternating helix-strand structures (beta-alpha-beta). Yeast also has significantly more helical membrane proteins than the other two genomes, with most of the differences concentrated in proteins containing two transmembrane segments. Comparison of tertiary structure (by sequence matching and domain-level clustering) highlights the substantial duplication in each genome (approximately 30% to 50%), with the degree of duplication following similar patterns in all three. Many sequence families are shared among the genomes, with the degree of overlap between any two genomes being roughly similar. In total, the three genomes contain 148 of the approximately 300 known protein folds. Forty-five of these 148 that are present in all three genomes are especially enriched in mixed super-secondary structures (alpha/beta). Moreover, the five most common of these 45 (the "top-5") have a remarkably similar super-secondary structure architecture, containing a central sheet of parallel strands with helices packed onto at least one face and beta-alpha-beta connections between adjacent strands. These most basic molecular parts, which, presumably, were present in the last common ancestor to the three Kingdoms, include the TIM-barrel, Rossmann, flavodoxin, thiamin-binding, and P-loop-hydrolase folds.
J Mol Biol 1997 Dec 12
PMID:A structural census of genomes: comparing bacterial, eukaryotic, and archaeal genomes in terms of protein structure. 941 35


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