Nitrophorins are hemoproteins found in the saliva of blood-feeding insects. Saliva of the blood-sucking bug Rhodnius prolixus contains at least seven homologous nitrophorins, designated NP1 to NP7 in order of their relative abundance in the glands. As isolated, nitrophorins contain nitric oxide (NO) ligated to the ferric heme iron (Fe3+). Histamine, which is released by the host in response to tissue damage, is another nitrophorin ligand. Nitrophorins transport NO to the feeding site. Dilution, binding of histamine and increase in pH (from pH ~5 in salivary gland to pH ~7.4 in the host tissue) facilitate the release of NO into the tissue where it induces vasodilatation.[1]
The salivary nitrophorin from the hemipteranCimex lectularius (bedbug) has no sequence similarity to Rhodnius prolixus nitrophorins but is homologous to the inositol-polyphosphate 5-phosphatase (EC 3.1.3.56). It is suggested that the two classes of insect nitrophorins have arisen as a product of the convergent evolution.
The crystal structures of several nitrophorin complexes are known. The Rhodnius prolixus nitrophorin structures reveal lipocalin-like eight-stranded β-barrel, three α-helices and two disulfide bonds, with heme inserted into one end of the barrel. Members of the lipocalin family are known to bind a variety of small hydrophobic ligands, including biliverdin, in a similar fashion. The heme iron is ligated to histidine residue (His-59). The position of His-59 is restrained through water-mediated hydrogen bond to the carboxylate of aspartic acid residue (Asp-70). The His-59–Fe bond is bent ~15° out of the imidazole plane. Asp-70 forms an unusual hydrogen bond with one of the heme propionates, suggesting the residue has an altered pKa. In NP1-histamine structure, the planes of His-59 and histamine imidazole rings lie in an arrangement almost identical to that found in oxidized cytochrome b5.
The fold of nitrophorin from Cimex lectularius consists of central 11-stranded β-sandwich and seven peripheral α-helices. The heme is positioned between β-sheet and an α-helix, with heme iron ligated to cysteinate residue. NO can bind both to heme Fe3+ and to proximal Cys-60 ligand causing reversible S-nitrosylation.
Referencesedit
^Walker, F. A. (2005). "Nitric Oxide Interaction with Insect Nitrophorins and Thoughts on the Electron Configuration of the FeNO6 complex". J. Inorg. Biochem. 99 (1): 216–236. doi:10.1016/j.jinorgbio.2004.10.009. PMID 15598503.
External links and further readingedit
Montfort, W.R., Weichsel, A. and Andersen, J.F. (2000). "Nitrophorins and related antihemostatic lipocalins from Rhodnius prolixus and other blood-sucking arthropods". Biochim. Biophys. Acta. 1482 (1–2): 110–118. doi:10.1016/S0167-4838(00)00165-5. PMID 11058753.{{cite journal}}: CS1 maint: multiple names: authors list (link)
Valenzuela, J.G. & Ribeiro, J.M.C. (1998). "Purification and cloning of the salivary nitrophorin from the hemipteran Cimex lectularius". J. Exp. Med. 201 (Pt 18): 2659–2664. doi:10.1242/jeb.201.18.2659. PMID 9716517.
Weichsel, A., Maes, E.M., Andersen, J.F., Valenzuela, J.G., Shokhireva, T.Kh., Walker, F.A. and Montfort, W.R. (2005). "Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein". Proc. Natl. Acad. Sci. USA. 102 (3): 594–599. Bibcode:2005PNAS..102..594W. doi:10.1073/pnas.0406549102. PMC545542. PMID 15637157.{{cite journal}}: CS1 maint: multiple names: authors list (link)
PDB: 1NP1 - X-ray structure of Rhodnius prolixus nitrophorin 1 complexed with histamine and PO43−
PDB: 1Y21 - X-ray structure of Cimex lectularius nitrophorin in complex with NO
Montfort Lab - Nitrophorin research @ University of Arizona, Tucson, USA
January 01, 1970
nitrophorin, hemoproteins, found, saliva, blood, feeding, insects, saliva, blood, sucking, rhodnius, prolixus, contains, least, seven, homologous, nitrophorins, designated, order, their, relative, abundance, glands, isolated, nitrophorins, contain, nitric, oxi. Nitrophorins are hemoproteins found in the saliva of blood feeding insects Saliva of the blood sucking bug Rhodnius prolixus contains at least seven homologous nitrophorins designated NP1 to NP7 in order of their relative abundance in the glands As isolated nitrophorins contain nitric oxide NO ligated to the ferric heme iron Fe3 Histamine which is released by the host in response to tissue damage is another nitrophorin ligand Nitrophorins transport NO to the feeding site Dilution binding of histamine and increase in pH from pH 5 in salivary gland to pH 7 4 in the host tissue facilitate the release of NO into the tissue where it induces vasodilatation 1 The salivary nitrophorin from the hemipteran Cimex lectularius bedbug has no sequence similarity to Rhodnius prolixus nitrophorins but is homologous to the inositol polyphosphate 5 phosphatase EC 3 1 3 56 It is suggested that the two classes of insect nitrophorins have arisen as a product of the convergent evolution The crystal structures of several nitrophorin complexes are known The Rhodnius prolixus nitrophorin structures reveal lipocalin like eight stranded b barrel three a helices and two disulfide bonds with heme inserted into one end of the barrel Members of the lipocalin family are known to bind a variety of small hydrophobic ligands including biliverdin in a similar fashion The heme iron is ligated to histidine residue His 59 The position of His 59 is restrained through water mediated hydrogen bond to the carboxylate of aspartic acid residue Asp 70 The His 59 Fe bond is bent 15 out of the imidazole plane Asp 70 forms an unusual hydrogen bond with one of the heme propionates suggesting the residue has an altered pKa In NP1 histamine structure the planes of His 59 and histamine imidazole rings lie in an arrangement almost identical to that found in oxidized cytochrome b5 The fold of nitrophorin from Cimex lectularius consists of central 11 stranded b sandwich and seven peripheral a helices The heme is positioned between b sheet and an a helix with heme iron ligated to cysteinate residue NO can bind both to heme Fe3 and to proximal Cys 60 ligand causing reversible S nitrosylation References edit Walker F A 2005 Nitric Oxide Interaction with Insect Nitrophorins and Thoughts on the Electron Configuration of the FeNO6 complex J Inorg Biochem 99 1 216 236 doi 10 1016 j jinorgbio 2004 10 009 PMID 15598503 External links and further reading editMontfort W R Weichsel A and Andersen J F 2000 Nitrophorins and related antihemostatic lipocalins from Rhodnius prolixus and other blood sucking arthropods Biochim Biophys Acta 1482 1 2 110 118 doi 10 1016 S0167 4838 00 00165 5 PMID 11058753 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link Valenzuela J G amp Ribeiro J M C 1998 Purification and cloning of the salivary nitrophorin from the hemipteran Cimex lectularius J Exp Med 201 Pt 18 2659 2664 doi 10 1242 jeb 201 18 2659 PMID 9716517 Weichsel A Maes E M Andersen J F Valenzuela J G Shokhireva T Kh Walker F A and Montfort W R 2005 Heme assisted S nitrosation of a proximal thiolate in a nitric oxide transport protein Proc Natl Acad Sci USA 102 3 594 599 Bibcode 2005PNAS 102 594W doi 10 1073 pnas 0406549102 PMC 545542 PMID 15637157 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link PDB 1NP1 X ray structure of Rhodnius prolixus nitrophorin 1 complexed with histamine and PO43 PDB 1Y21 X ray structure of Cimex lectularius nitrophorin in complex with NO Montfort Lab Nitrophorin research University of Arizona Tucson USA Retrieved from https en wikipedia org w index php title Nitrophorin amp oldid 1222163128, wikipedia, wiki, book, books, library,
