1ywd
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(New page: 200px<br /><applet load="1ywd" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ywd, resolution 1.08Å" /> '''1.08 A Structure of ...)
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Revision as of 04:58, 21 November 2007
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1.08 A Structure of Ferrous NP4 (aquo complex)
Overview
Nitrophorin 4 (NP4), a nitric oxide (NO)-transport protein from the, blood-sucking insect Rhodnius prolixus, uses a ferric (Fe3+) heme to, deliver NO to its victims. NO binding to NP4 induces a large, conformational change and complete desolvation of the distal pocket. The, heme is markedly nonplanar, displaying a ruffling distortion postulated to, contribute to stabilization of the ferric iron. Here, we report the, ferrous (Fe2+) complexes of NP4 with NO, CO, and H2O formed after chemical, reduction of the protein and the characterization of these complexes by, absorption spectroscopy, flash photolysis, and ultrahigh-resolution, crystallography (resolutions vary from 0.9 to 1.08 A). The absorption, spectra, both in solution and in the crystal, are typical for, six-coordinated ferrous complexes. Closure and desolvation of the distal, pocket occurs upon binding CO or NO to the iron regardless of the heme, oxidation state, confirming that the conformational change is driven by, distal ligand polarity. The degree of heme ruffling is coupled to the, nature of the ligand and the iron oxidation state in the following order:, (Fe3+)-NO > (Fe2+)-NO > (Fe2+)-CO > (Fe3+)-H2O > (Fe2+)-H2O. The ferrous, coordination geometry is as expected, except for the proximal histidine, bond, which is shorter than typically found in model compounds. These data, are consistent with heme ruffling and coordination geometry serving to, stabilize the ferric state of the nitrophorins, a requirement for their, physiological function. Possible roles for heme distortion and NO bending, in heme protein function are discussed.
About this Structure
1YWD is a Single protein structure of sequence from Rhodnius prolixus with HEM as ligand. Full crystallographic information is available from OCA.
Reference
Ultrahigh resolution structures of nitrophorin 4: heme distortion in ferrous CO and NO complexes., Maes EM, Roberts SA, Weichsel A, Montfort WR, Biochemistry. 2005 Sep 27;44(38):12690-9. PMID:16171383
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