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)

The PTH/PTH-related peptide receptor is a member of a newly discovered family of G-protein-coupled receptors. Strikingly conserved features among these receptors include the positioning of eight extracellular cysteines and several other residues that are located predominantly within the membrane-embedded region. Deletion mutants or receptors with point mutations of the highly conserved cysteine residues were transiently expressed in COS-7 cells to evaluate PTH binding and PTH-stimulated cAMP production. Deletion of residues 61-105, which are encoded by exon E2 in the PTH/PTH-related peptide receptor gene, did not affect receptor function. An epitope derived from Haemophilus influenza hemagglutinin was, therefore, introduced into this portion of most receptors to allow the independent assessment of cell surface expression. PTH binding capacity was not reduced by the deletion of residues 258-278 in the first extracellular loop. Receptors with deletion of either residues 31-47 in the amino-terminal extension or residues 431-440 in the third extracellular loop failed to bind PTH, although expression of the receptor on the cell surface was only marginally reduced. Most other receptor mutants, including those in which each of the six cysteines in the amino-terminus was replaced by serines, failed to be processed and/or expressed appropriately, whereas the substitution of cysteine-281 or -351 had a less severe effect. The combined replacement of both cysteines concomitantly increased PTH binding and cell surface expression, suggesting the formation of a disulfide bond between these two residues. Our data indicate that residues near the amino-terminus and within the third extracellular loop are necessary for ligand binding, whereas more than 25% of the receptor's extracellular region appears not to be involved.
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PMID:Role of the extracellular regions of the parathyroid hormone (PTH)/PTH-related peptide receptor in hormone binding. 752 99

P6 is an outer membrane protein of Haemophilus influenzae that is antigenically conserved and considered a candidate component of future H. influenzae vaccines. P6 contains a surface-exposed epitope recognized by monoclonal antibody (MAb) 3B9. This epitope has been shown to be distinct from that recognized by the P6-specific MAbs 7F3 and 4G4 in a competitive inhibition enzyme-linked immunosorbent assay (ELISA). MAb 3B9 did not bind to synthetic P6-specific sequential and overlapping hexameric peptides. Five peptides made to correspond to P6 sequences with high probabilities of surface exposure did not inhibit binding of MAb 3B9 to P6. An antiserum to one of the peptides, designated SP66, inhibited binding of MAb 3B9 to P6. A rabbit antiserum to P6 bound to sequential hexameric peptides, Gly-87AsnThrAspGluArgGlyThr-94, which were in the SP66 region of P6. This antiserum inhibited the binding of P6 to MAb 3B9 in a competitive inhibition ELISA. P6 mutations with His and Ala substitutions at residues Thr-88 and Asn-89 still bound MAb 3B9. MAb 3B9 reacted with Escherichia coli OmpA and Salmonella typhimurium OmpA. Sequence comparisons of P6 with these proteins indicated that the residue in the SP66 region responsible for binding is either Gly-87, Asp-90, or Gly-93. Mercaptoethanol reduction abolished MAb 3B9 binding to E. coli OmpA and S. typhimurium OmpA. In these proteins, immediately downstream of the second cysteine, there is an ArgArg dipeptide which is identical to and aligns with Arg-147Arg-148 in P6. This dipeptide has a high probability of surface exposure in P6. Mutagenesis of the Arg-147Arg-148 to an AlaAla dipeptide in P6 abolished binding of MAb 3B9, demonstrating that it was either a portion of the epitope or important in the protein folding necessary for expression of this epitope. This study demonstrates that MAb 3B9 recognizes a conserved conformational determinant on the surface of H. influenzae that is composed of two discontinuous regions of P6.
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PMID:Mapping of a surface-exposed, conformational epitope of the P6 protein of Haemophilus influenzae. 759 Oct 76

Seven cultures referred to in our laboratories as unidentified gram-negative bacilli or Haemophilus species were identified as atypical strains of Francisella tularensis lacking a requirement for cysteine or enriched medium for growth. The use of cellular fatty acid composition analysis facilitated early recognition of this pathogen and prompt implementation of appropriate biosafety measures.
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PMID:Early recognition of atypical Francisella tularensis strains lacking a cysteine requirement. 815 Sep 73

Haemophilus ducreyi contains a major outer membrane protein (MOMP) whose apparent molecular weight is 39,000 to 42,000 for all strains tested. Two monoclonal antibodies (MAbs), designated 9D12 and 2C7, bound to the MOMP for all strains of H. ducreyi tested. As reported previously, MAb 9D12 was H. ducreyi specific (E. J. Hansen and T. A. Loftus, Infect. Immun. 44:196-198, 1984). MAb 2C7 bound to all members of the family Pasteurellaceae tested, suggesting that the MAbs bound to distinct epitopes on the MOMP. The MOMP was purified by extraction of whole cells with Zwittergent and ion-exchange chromatography. A peak eluted from a cation-exchange column contained three bands. All three species bound both MAbs, and the fraction yielded a single N-terminal amino acid sequence, suggesting that the bands represented different conformations of the MOMP. The MOMP was heat modifiable, contained two cysteine residues, and was cationic at pH 8.0, features not usually associated with classical porin proteins. The N-terminal amino acid sequence and total amino acid content of the MOMP were homologous to the OmpA proteins of members of the family Enterobacteriaceae and the OmpA-like protein of Actinobacillus actinomycetemcomitans. An OmpA-specific polyclonal serum bound to the MOMP, and MAb 2C7 bound to Haemophilus influenzae protein 5, an OmpA-like protein, indicating that the MOMP was antigenically related to OmpA. These data indicated that the most abundant protein in the outer membrane of H. ducreyi was not a classical porin and belonged to the OmpA family of proteins.
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PMID:The major outer membrane protein of Haemophilus ducreyi is a member of the OmpA family of proteins. 845 37

The roles of disulfide and sulfhydryl groups in the specific binding of TRH to its receptor have been examined. In all TRH receptors (TRH-Rs) isolated from different species so far, there are only two extracellular cysteine residues (Cys98 in the extracellular loop between transmembrane helices 2 and 3 and Cys179 in the extracellular loop between transmembrane helices 4 and 5) that are in positions homologous to cysteine residues in other G protein-coupled receptors. Another Cys (Cys100) is located in close proximity to Cys98 at the interface between the first extracellular loop and third transmembrane domain. To assess the role of these TRH-R Cys residues in disulfide bonding interactions, they were mutated to either Ser or Ala. Six mutant receptors (Cys98Ser, Cys98Ala, Cys179Ser, Cys179Ala, Cys100Ser, and Cys100Ala) were expressed in COS-1 cells and tested for their ability to bind TRH and to activate total inositol phosphate (IP) formation. TRH-R mutants Cys100Ser and Cys100Ala showed TRH binding affinities and IP activation similar to the wild-type (WT). In contrast, mutants Cys98Ser, Cys98Ala, Cys179Ser, and Cys179Ala showed no high affinity TRH binding. The potencies of Cys98Ala and Cysl79Ala as measured by IP stimulation were decreased by four orders of magnitude when compared with WT. Cys98Ser potency decreased by five orders of magnitude, whereas Cys179Ser showed no IP production. Northern blotting confirmed expression of all the mutant TRH-Rs at the messenger RNA (mRNA) level. An epitope tag derived from the Haemophilus influenza hemagglutinin protein was incorporated at the NH2 termini of the TRH-R WT and TRH-R Cys mutants to allow the independent assessment of cell surface expression of receptor protein. TRH-R mutants that failed to show receptor binding (Cys98Ser, Cys98Ala, Cys179Ala) showed WT levels of cell surface receptor expression, indicating that loss of receptor binding in these mutants is not attributable to loss of receptor expression. In contrast, cell surface expression of Cysl79Ser, which showed no ligand induced IP stimulation, could not be detected. Dithiothreitol, a disulfide bond reducing agent, and p-chloromercuribenzoic acid (p-CMB), a sulfhydryl blocking compound, reduced specific TRH binding in a dose-dependent manner. The inhibition of binding by dithiothreitol implies that the integrity of a disulfide bond is important for TRH binding to its receptor. The dramatic inhibition of TRH binding by p-CMB indicates that free sulfhydryl groups are also associated with the binding of the ligand to its receptor. This study presents evidence that a disulfide bond exists between Cys98 and Cys179 which is essential for maintaining the receptor in the correct conformation for ligand binding. Cys100 is not thought to have a disulfide bonding interaction role. Results obtained after chemical modification have shown that free sulfhydryl groups within the TRH-R may also have a role in ligand interactions.
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PMID:A disulfide bonding interaction role for cysteines in the extracellular domain of the thyrotropin-releasing hormone receptor. 877 Sep 6

A novel thioredoxin-linked thiol peroxidase (Px) from Escherichia coli has been reported previously (M. K. Cha, H. K. Kim, and I. H. Kim, J. Biol. Chem. 270:28635-28641, 1995). In an attempt to perform physiological and biochemical characterizations of the thiol Px, a thiol Px null (tpx) mutant and a functional-residue mutant of thiol Px were produced. The tpx mutant was viable in aerobic culture but grew more slowly than the wild-type cells. The difference in growth rate became more pronounced when oxidative-stress-inducing reagents, such as peroxides and paraquat, were added to the cultures. The viability of the individual tpx mutant under oxidative stress was much lower than that of wild-type cells. tpx mutants growing aerobically respond to paraquat with a sixfold greater induction of Mn-superoxide dismutase than that of the wild-type cells. The deduced amino acid sequence of the thiol Px was found to be from 42 to 72% identical to the sequences of proteins from Haemophilus influenzae (ToxR regulon), Vibrio cholerae (ToxR regulon), and three kinds of streptococci (coaggregation-mediating adhesins), suggesting that they all belong to a new thiol Px family. Alignment of the amino acid sequences of the thiol Px family members showed that one cysteine, which corresponds to Cys-94 in E. coli thiol Px, is perfectly conserved. The substitution of serine for this cysteine residue resulted in complete loss of Px activity. These results suggest that the members of the thiol Px family, including E. coli thiol Px, have a functional cysteine residue and function in vivo as peroxidases.
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PMID:Mutation and Mutagenesis of thiol peroxidase of Escherichia coli and a new type of thiol peroxidase family. 882 4

Frozen sections of chinchilla Eustachian tube (ET) and middle ear mucosa were incubated with either FITC-labeled non-typeable Haemophilus influenzae (NTHi) or Bordetella pertussis. The number of bacteria adherent to "roof" vs "floor" regions was compared for each of three anatomic portions of the ET and for middle ear epithelium noting whether bacteria adhered to mucus or to epithelial cells. NTHi strains adhered significantly greater to mucus in the ET lumen whereas B. pertussis preferentially adhered to epithelial cells lining the ET (P < or = 0.05). A non-fimbriated isogenic mutant of NTHi adhered significantly less to mucus than the parental isolate at all sites of the ET floor (P < or = 0.05). Isolated fimbrin protein adhered to ET mucus and blocked adherence of whole organisms. Treatment with the mucolytic agent N-acetyl-L-cysteine resulted in significantly reduced adherence of NTHi to mucus (P < or = 0.001) and eliminated the ability to detect binding of isolated fimbrin protein. N-acetyl-L-cysteine treatment did not affect adherence of either B. pertussis or NTHi to epithelial cells. These data indicated that NTHi may mediate ascension of the ET from the nasopharynx primarily via adherence to and growth in mucus overlying the floor region of the tubal lumen. The OMP P5-homologous fimbriae were shown to contribute to this binding.
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PMID:Selective adherence of non-typeable Haemophilus influenzae (NTHi) to mucus or epithelial cells in the chinchilla eustachian tube and middle ear. 893 42

A simple procedure for conjugating synthetic fragments of the capsular polysaccharide of Haemophilus influenzae type b, poly-3-beta-D-ribose-(1,1)-D-ribitol-5-phosphate (sPRP) to linear peptides is described. The procedure consists of (i) reacting the amino group of amino-heptyl sPRP with m-maleimidobenzoyl-N-hydroxysuccinimide (MBS) in phosphate buffer, pH 7.5; (ii) selectively coupling the MBS-modified sPRP to the sulfhydryl group of the cysteine residue of peptides containing functional T-helper cell epitope(s). The glycopeptide conjugates were purified by gel filtration chromatography, biochemically characterized, and elicited protective level of anti-PRP antibody responses in rabbits.
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PMID:Chemical synthesis of Haemophilus influenzae glycopeptide conjugates. 907 9

Thermus thermophilus peptide deformylase was characterized. Its enzymatic properties as well as its organization in domains proved to share close resemblances with those of the Escherichia coli enzyme despite few sequence identities. In addition to the HEXXH signature sequence of the zinc metalloprotease family, a second short stretch of strictly conserved amino acids was noticed, EGCLS, the cysteine of which corresponds to the third zinc ligand. The study of site-directed mutants of the E. coli deformylase shows that the residues of this stretch are crucial for the structure and/or catalytic efficiency of the active enzyme. Both aforementioned sequences were used as markers of the peptide deformylase family in protein sequence databases. Seven sequences coming from Haemophilus influenzae, Lactococcus lactis, Bacillus stearothermophilus, Mycoplasma genitalium, Mycoplasma pneumoniae, Bacillus subtilus and Synechocystis sp. could be identified. The characterization of the product of the open reading frame from B. stearothermophilus confirmed that it actually corresponded to a peptide deformylase with properties similar to those of the E. coli enzyme. Alignment of the nine peptide deformylase sequences showed that, in addition to the two above sequences, only a third one, GXGXAAXQ, is strictly conserved. This motif is also located in the active site according to the three-dimensional structure of the E. coli enzyme. Site-directed variants of E. coli peptide deformylase showed the involvement of the corresponding residues for maintaining an active and stable enzyme. Altogether, these data allow us to propose that the three identified conserved motifs of peptide deformylases build up the active site around a metal ion. Finally, an analysis of the location of the other conserved residues, in particular of the hydrophobic ones, was performed using the three-dimensional model of the E. coli enzyme. This enables us to suggest that all bacterial peptide deformylases adopt a constant overall tertiary structure.
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PMID:Structure-function relationships within the peptide deformylase family. Evidence for a conserved architecture of the active site involving three conserved motifs and a metal ion. 912 50

Whereas mammalian cells produce PS by a base exchange reaction from preexisting phospholipids, yeast cells synthesize PS from CDP-diacylglycerol and serine by the PS synthase reaction. Yeast PS synthase was purified to homogeneity and shown to have a molecular mass of 23 kDa. The activity is dependent on either Mg2+ or Mn2+ and Triton X-100. The enzyme specifically transfers the phosphatidyl group from CDP-diacylglycerol or dCDP-diacylglycerol to L-serine, but not to threonine, cysteine and ethanolamine. The PSS/CHO1 gene encoding the enzyme was cloned by the complementation of the choline auxotrophic pss/cho1 mutant. The deduced protein comprises 279 amino acids with a calculated molecular mass of 30,804. The primary translate undergoes proteolytic processing to the enzymatically more active 23-kDa enzyme. The deduced amino acid sequence contains several putative membrane-spanning regions and resembles that of the Bacillus subtilis enzyme, but not those of the E. coli and Haemophilus influenzae enzymes. The sequence also contains the local, conserved region found in enzymes catalyzing the transfer of the phosphoalcohol moiety from CDP-alcohol, such as PI synthase, cholinephosphotransferase and phosphatidylglycerolphosphate synthase. The activity of PS synthase is maximal in the exponential phase, but decreases when cells enter the stationary phase. The enzyme is phosphorylated at a single serine residue by cyclic AMP-dependent protein kinase with a 60-70% decrease in enzymatic activity, but the primary translation product is not phosphorylated. PS synthase is inhibited by CTP, probably due to the chelation of the divalent cations, Mg2+ and Mn2+, and also by sphingoid bases, such as sphinganine and phytosphingosine. Phosphatidate, phosphatidylcholine and phosphatidylinositol are stimulatory, whereas cardiolipin and diacylglycerol are inhibitory. The expression of yeast PS synthase is transcriptionally repressed by myo-inositol and choline in a coordinate manner with other phospholipid-synthesizing enzymes. The upstream regulatory region of the PSS/CHO1 gene responsible for the myo-inositol-choline regulation was identified. An octameric sequence, CATRTGAA (R = A or G), plays an important role in the conferral of the myo-inositol-choline transcriptional regulation.
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PMID:Phosphatidylserine synthase from yeast. 937 Mar 37


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