1x8p | pdb_00001x8p

0.85 A Crystal Structure Of Nitrophorin 4 From Rhodnius Prolixus Complexed With Ammonia at pH 7.4

spinqualitylabelsall models 1x8p, resolution 0.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1x8p is a 1 chain structure with sequence from Rhodnius prolixus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: HEM, NH3 Related: 1d2u, 1x8n, 1x8o, 1x8q Resources: FirstGlance, OCA, RCSB, PDBsum 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 PubMed The blood-sucking insect Rhodnius prolixus uses nitrophorin 4, a heme protein, to deliver nitric oxide (NO) to a victim, causing vasodilation and improved feeding. Binding of NO occurs at a ferric heme and is modulated by pH. NO binding at lower pH induces a large conformational change involving loops A-B and G-H that leads to distal pocket desolvation and protection of the nitrosyl heme complex. We have determined the crystal structures of Rhodnius nitrophorin 4 to ultrahigh resolution in four functional states: +/-NO at pH = 7.4 and +/-NO at pH = 5.6. The structure with NO at pH 7.4 (1.08 A) is newly determined while the other complexes have been modeled to resolutions much greater than previously reported (1.0-0.85 A). The ultrahigh resolution allowed us to resolve multiple conformers in binding-site loops, leading to a detailed description of the dynamics involved with storing NO in the insect salivary gland at low pH, and releasing NO in response to the increased pH of a victim's tissue. Strikingly, features for both the "open" and "closed" conformers exist under all conditions, suggesting that the flexible loops can transition with relative ease between conformational states. Yet, release of NO from rNP4 is much slower than found for other ferric heme proteins. The structures suggest that highly mobile loops can limit diffusion of diatomic molecules into and out of a protein cavity, a result with implications for the role of protein dynamics in function. Protein functional cycle viewed at atomic resolution: conformational change and mobility in nitrophorin 4 as a function of pH and NO binding.,Kondrashov DA, Roberts SA, Weichsel A, Montfort WR Biochemistry. 2004 Nov 2;43(43):13637-47. PMID:15504026 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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