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

Heme can serve Haemophilus influenzae as a source of both essential porphyrin and iron. In extracellular mammalian body fluids neither free heme nor free iron is available, since they are tightly bound to hemopexin and transferrin, respectively. Since H. influenzae grows in the presence of iron-transferrin and heme-hemopexin and is known to express a saturable receptor for transferrin, we investigated the process by which this pathogen acquired heme from hemopexin for use as an iron source. The ability of human and rabbit hemopexin to donate heme as a source of iron to H. influenzae type b strains was demonstrated by plate bioassays. With a dot enzyme assay with biotinylated hemopexin as ligand, H. influenzae bound heme-hemopexin and apo-hemopexin following growth in iron-restricted, but not in iron-sufficient, medium. Competitive binding studies with heme-hemopexin and apo-hemopexin demonstrated saturability of binding. Neither heme, protoporphyrin IX, hemoglobin, nor transferrin blocked the binding of hemopexin to whole cells, demonstrating the specificity of binding. Treatment of whole H. influenzae cells with trypsin abolished binding. Taken together, these observations suggest that H. influenzae type b expresses an outer membrane protein(s) which acts as a receptor for hemopexin and which is regulated by the availability of iron in the growth medium. In iron-restricted media, H. influenzae 706705 and DL42 did not express the 100-kDa hemopexin-binding protein previously reported (M.S. Hanson, S.E. Pelzel, J. Latimer, U. Muller-Eberhard, and E.J. Hansen, Proc. Natl. Acad. Sci. USA 89:1973-1977, 1992). The putative iron-regulated hemopexin receptor was solubilized from cell envelopes of H. influenzae 706705, DL42, and Eagan with the detergent CHAPS (3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate) and isolated by affinity chromatography on heme-hemopexin-Sepharose 4B. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins bound to the affinity resin revealed three proteins of 29, 38, and 57 kDa, of which the 57- and 29-kDa proteins bound hemopexin after Western blotting (immunoblotting). A monoclonal antibody to the 57-kDa hemopexin-binding protein of 706705 recognized a 57-kDa protein on Western blots of the cell envelope proteins of 706705, DL42, and Eagan; no reaction was observed with the 100-kDa hemopexin-binding protein of DL42. These data suggest that some H. influenzae strains possess at least two hemopexin receptors, the expression of which is determined by the prevailing growth environment.
 ...
PMID:Identification and characterization of an iron-regulated hemopexin receptor in Haemophilus influenzae type b. 826 49

The solubilization of a particular protein is mandatory for its subsequent resolution and detection in two-dimensional gels. However, the extraction solutions, that are compatible with the first-dimensional separation step, such as urea and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), do not solubilize all proteins in a sample. We studied the effect of various common, strong detergents and chaotropes, widely used as solubilizing agents, such as sodium dodecyl sulfate, lithium dodecyl sulfate and guanidine hydrochloride, on the solubilization of the total and membrane proteins of the bacterium Haemophilus influenzae. The proteins solubilized with each system were analyzed by two-dimensional electrophoresis and these of interest were identified by matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS). Use of sodium dodecyl sulfate, lithium dodecyl sulfate or guanidine hydrochloride for the solubilization of total proteins of the microorganism resulted in the detection of several additional spots, representing mainly outer membrane proteins, in comparison with those detected in the soluble protein fraction. Solubilization of the proteins of the cell envelope fraction with sodium dodecyl sulfate did not result in a more efficient protein detection when compared to the extraction with the urea/CHAPS system. When the dry immobilized pH gradient strips were rehydrated in a solution containing the proteins of the membrane fraction solubilized with sodium dodecyl sulfate or lithium dodecyl sulfate, a larger number of protein spots were detected in comparison with strips that were rehydrated in the urea/CHAPS solution. However, no improvement was observed in comparison with protein application in sample cups. The additional proteins detected with the use of strong detergents and chaotropes are in the majority difficult to solubilize and less hydrophobic proteins.
 ...
PMID:Effect of strong detergents and chaotropes on the detection of proteins in two-dimensional gels. 1142 15