1U0X
Crystal structure of nitrophorin 4 under pressure of xenon (200 psi)
Summary for 1U0X
| Entry DOI | 10.2210/pdb1u0x/pdb |
| Related | 1D2U 1KOI |
| Descriptor | Nitrophorin 4, PROTOPORPHYRIN IX CONTAINING FE, AMMONIA, ... (5 entities in total) |
| Functional Keywords | beta-barrel, lipocalin, ferric heme, xenon, transport protein |
| Biological source | Rhodnius prolixus |
| Cellular location | Secreted: Q94734 |
| Total number of polymer chains | 1 |
| Total formula weight | 21188.77 |
| Authors | Nienhaus, K.,Maes, E.M.,Weichsel, A.,Montfort, W.R.,Nienhaus, G.U. (deposition date: 2004-07-14, release date: 2004-07-20, Last modification date: 2024-11-06) |
| Primary citation | Nienhaus, K.,Maes, E.M.,Weichsel, A.,Montfort, W.R.,Nienhaus, G.U. Structural dynamics controls nitric oxide affinity in nitrophorin 4 J.Biol.Chem., 279:39401-39407, 2004 Cited by PubMed Abstract: Nitrophorin 4 (NP4) is one of seven nitric oxide (NO) transporting proteins in the blood-sucking insect Rhodnius prolixus. In its physiological function, NO binds to a ferric iron centered in a highly ruffled heme plane. Carbon monoxide (CO) also binds after reduction of the heme iron. Here we have used Fourier transform infrared spectroscopy at cryogenic temperatures to study CO and NO binding and migration in NP4, complemented by x-ray cryo-crystallography on xenon-containing NP4 crystals to identify cavities that may serve as ligand docking sites. Multiple infrared stretching bands of the heme-bound ligands indicate different active site conformations with varying degrees of hydrophobicity. Narrow infrared stretching bands are observed for photodissociated CO and NO; temperature-derivative spectroscopy shows that these bands are associated with ligand docking sites close to the extremely reactive heme iron. No rebinding from distinct secondary sites was detected, although two xenon binding cavities were observed in the x-ray structure. Photolysis studies at approximately 200 K show efficient NO photoproduct formation in the more hydrophilic, open NP4 conformation. This result suggests that ligand escape is facilitated in this conformation, and blockage of the active site by water hinders immediate reassociation of NO to the ferric iron. In the closed, low-pH conformation, ligand escape from the active site of NP4 is prevented by an extremely reactive heme iron and the absence of secondary ligand docking sites. PubMed: 15258143DOI: 10.1074/jbc.M406178200 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.45 Å) |
Structure validation
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