Ultrahigh resolution structures of nitrophorin 4: Heme distortion in ferrous CO and NO complexes

Estelle M. Maes, Sue A Roberts, Andrzej Weichsel, William "Bill" Montfort

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

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 Å). 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 > (Fe 2+)-CO > (Fe3+)-H2O > (Fe 2+)-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.

Original languageEnglish (US)
Pages (from-to)12690-12699
Number of pages10
JournalBiochemistry
Volume44
Issue number38
DOIs
StatePublished - Sep 27 2005

Fingerprint

Carbon Monoxide
Heme
Nitric Oxide
Iron
Rhodnius
Ligands
Hemeproteins
Oxidation
Crystallography
Geometry
nitrophorin
ferrous oxide
Photolysis
Absorption spectroscopy
Histidine
Insects
Absorption spectra
Spectrum Analysis
Carrier Proteins
Blood

ASJC Scopus subject areas

  • Biochemistry

Cite this

Ultrahigh resolution structures of nitrophorin 4 : Heme distortion in ferrous CO and NO complexes. / Maes, Estelle M.; Roberts, Sue A; Weichsel, Andrzej; Montfort, William "Bill".

In: Biochemistry, Vol. 44, No. 38, 27.09.2005, p. 12690-12699.

Research output: Contribution to journalArticle

@article{1eb0f6d1b7af4ffc8e699f0cea5b3e33,
title = "Ultrahigh resolution structures of nitrophorin 4: Heme distortion in ferrous CO and NO complexes",
abstract = "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 {\AA}). 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 > (Fe 2+)-CO > (Fe3+)-H2O > (Fe 2+)-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.",
author = "Maes, {Estelle M.} and Roberts, {Sue A} and Andrzej Weichsel and Montfort, {William {"}Bill{"}}",
year = "2005",
month = "9",
day = "27",
doi = "10.1021/bi0506573",
language = "English (US)",
volume = "44",
pages = "12690--12699",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "38",

}

TY - JOUR

T1 - Ultrahigh resolution structures of nitrophorin 4

T2 - Heme distortion in ferrous CO and NO complexes

AU - Maes, Estelle M.

AU - Roberts, Sue A

AU - Weichsel, Andrzej

AU - Montfort, William "Bill"

PY - 2005/9/27

Y1 - 2005/9/27

N2 - 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 Å). 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 > (Fe 2+)-CO > (Fe3+)-H2O > (Fe 2+)-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.

AB - 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 Å). 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 > (Fe 2+)-CO > (Fe3+)-H2O > (Fe 2+)-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.

UR - http://www.scopus.com/inward/record.url?scp=25644434241&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=25644434241&partnerID=8YFLogxK

U2 - 10.1021/bi0506573

DO - 10.1021/bi0506573

M3 - Article

C2 - 16171383

AN - SCOPUS:25644434241

VL - 44

SP - 12690

EP - 12699

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 38

ER -