Fabianne Walker

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The bloodsucking bug Rhodnius prolixus has a salivary vasodilator, previously characterized as a nitrovasodilator, with salivary smooth muscle-relaxing and antiplatelet activity. Rhodnius salivary glands are bright red owing to the abundance of heme proteins. Electron paramagnetic resonance and optical spectroscopic experiments indicated that the salivary(More)
The salivary glands of Rhodnius prolixus contain a nitrosyl-heme protein, named nitrophorin, that releases the vasodilatory and antiplatelet compound nitric oxide (NO). Because imidazole compounds such as histamine can interact with Fe(III) heme proteins, we investigated whether such substances could interact with Rhodnius nitrophorins. Both imidazole and(More)
The de novo design of membrane proteins remains difficult despite recent advances in understanding the factors that drive membrane protein folding and association. We have designed a membrane protein PRIME (PoRphyrins In MEmbrane) that positions two non-natural iron diphenylporphyrins (Fe(III)DPP's) sufficiently close to provide a multicentered pathway for(More)
Nitrophorin 2 (NP2), one of the four NO-storing and NO-releasing proteins found in the saliva of the blood-sucking bug Rhodnius prolixus, has a more ruffled heme and a high preference for a particular heme orientation (B) compared with nitrophorin 1 and nitrophorin 4, which show not a preference (A to B ratio of approximately 1:1), suggesting that it fits(More)
The ferriheme resonances of the low-spin (S = 1/2) complexes of wild-type (wt) nitrophorin 2 (NP2) and its heme pocket mutant NP2(V24E) with imidazole (ImH), histamine (Hm), and cyanide (CN(-)) as the sixth ligand have been investigated by NMR spectroscopy as a function of pH (4.0-7.5). For the three wt NP2 complexes, the ratio of the two possible heme(More)
The β-barrel nitrophorin (NP) heme proteins are found in the saliva of the blood-sucking insect Rhodnius prolixus, which synthesizes and stores nitric oxide (NO) in the salivary glands. NO is bound to iron of the NPs and is released by dilution and an increase in pH when the insect spits its saliva into the tissues of a victim, to aid in obtaining a blood(More)
The nuclear Overhauser effects (NOEs) observed between heme substituent protons and a small number of nearby protein side chain protons in the water-elimination Fourier transform NOE spectroscopy (WEFT-NOESY) spectra of high- and low-spin wild-type nitrophorin (NP) 2 and its ligand complexes have been analyzed and compared with those observed for the same(More)
Nitrophorin 4, one of the four NO-carrying heme proteins from the salivary glands of Rhodnius prolixus, forms a homodimer at pH 5.0 with a Kd of ∼8 μM. This dimer begins to dissociate at pH 5.5 and is completely dissociated to monomer at pH 7.3, even at 3.7 mM. The dimer is significantly stabilized by binding NO to the heme and at pH 7.3 would require(More)