2hys
From Proteopedia
|
Crystal structure of nitrophorin 2 complexed with cyanide
Overview
In this work we report the assignment of the majority of the ferriheme, resonances of low-spin nitrophorins (NP) 1 and 4 and compare them to those, of NP2, published previously. It is found that the structure of the, ferriheme complexes of NP1 and NP4, in terms of the orientation of the, ligand(s), can be determined with good accuracy by NMR techniques in the, low-spin forms and that angle plots proposed previously (Shokhirev, N. V.;, Walker, F. A. J. Biol. Inorg. Chem. 1998, 3, 581-594) describe the angle, of the effective nodal plane of the axial ligands in solution. The, effective nodal plane of low-spin NP1, NP4, and NP2 complexes is in all, cases of imidazole and histamine complexes quite similar to the average of, the His-59 or -57 and the exogenous ligand angles seen in the X-ray, crystal structures. For the cyanide complexes of the nitrophorins, however, the effective nodal plane of the axial ligand does not coincide, with the actual histidine-imidazole plane orientation. This appears to be, a result of the contribution of an additional source of asymmetry, the, orientation of one of the zero-ruffling lines of the heme. Probably this, effect exists for the imidazole and histamine complexes as well, but, because the effect of asymmetry that occurs from planar exogenous axial, ligands is much larger than the effect of heme ruffling the effect of the, zero-ruffling line can only be detected for the cyanide complexes, where, the only ligand plane is that of the proximal histidine. The, three-dimensional structures of the three NP-CN complexes, including that, of NP2-CN reported herein, confirm the high degree of ruffling of these, complexes. There is an equilibrium between the two heme orientations (A, and B) that depends on the heme cavity shape and changes somewhat with, exogenous axial ligand. The A:B ratio can be much more accurately measured, by NMR spectroscopy than by X-ray crystallography.
About this Structure
2HYS is a Single protein structure of sequence from Rhodnius prolixus with CYN and HEM as ligands. Full crystallographic information is available from OCA.
Reference
Assignment of the ferriheme resonances of the low-spin complexes of nitrophorins 1 and 4 by (1)H and (13)C NMR spectroscopy: comparison to structural data obtained from X-ray crystallography., Shokhireva TKh, Weichsel A, Smith KM, Berry RE, Shokhirev NV, Balfour CA, Zhang H, Montfort WR, Walker FA, Inorg Chem. 2007 Mar 19;46(6):2041-56. Epub 2007 Feb 10. PMID:17290983
Page seeded by OCA on Wed Nov 21 12:03:39 2007
Categories: Rhodnius prolixus | Single protein | Montfort, W.R. | Weichsel, A. | CYN | HEM | Beta barrel | Cyanide | Ferric heme | Lipocalin
