1t68
Crystal structure of nitrophorin 2 complex with NO
Structural highlights
FunctionNP2_RHOPR Heme-based protein that deliver nitric oxide gas (NO) to the victim while feeding, resulting in vasodilation and inhibition of platelet aggregation. Also bind tightly to histamine, which is released by the host to induce wound healing (By similarity). Specifically inhibits factor IXa-catalyzed activation of factor X in the presence of calcium and phospholipids irrespective of the presence or absence of factor VIIIa. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNitrophorin 2 (NP2) (also known as prolixin-S) is a salivary protein that transports nitric oxide, binds histamine, and acts as an anticoagulant during blood feeding by the insect Rhodnius prolixus. The 2.0-A crystal structure of NP2 reveals an eight-stranded antiparallel beta-barrel containing a ferric heme coordinated through His(57), similar to the structures of NP1 and NP4. All four Rhodnius nitrophorins transport NO and sequester histamine through heme binding, but only NP2 acts as an anticoagulant. Here, we demonstrate that recombinant NP2, but not recombinant NP1 or NP4, is a potent anticoagulant; recombinant NP3 also displays minor activity. Comparison of the nitrophorin structures suggests that a surface region near the C terminus and the loops between beta strands B-C and E-F is responsible for the anticoagulant activity. NP2 also displays larger NO association rates and smaller dissociation rates than NP1 and NP4, which may result from a more open and more hydrophobic distal pocket, allowing more rapid solvent reorganization on ligand binding. The NP2 protein core differs from NP1 and NP4 in that buried Glu(53), which allows for larger NO release rates when deprotonated, hydrogen bonds to invariant Tyr(81). Surprisingly, this tyrosine lies on the protein surface in NP1 and NP4. The crystal structure of nitrophorin 2. A trifunctional antihemostatic protein from the saliva of Rhodnius prolixus.,Andersen JF, Montfort WR J Biol Chem. 2000 Sep 29;275(39):30496-503. PMID:010884386[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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