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Titolo:
Crystal structure of a nonsymbiotic plant hemoglobin
Autore:
Hargrove, MS; Brucker, EA; Stec, B; Sarath, G; Arredondo-Peter, R; Klucas, RV; Olson, JS; Phillips, GN;
Indirizzi:
Iowa State Univ Sci & Technol, Dept Biochem Biophys & Mol Biol, Ames, IA 50011 USA Iowa State Univ Sci & Technol Ames IA USA 50011 Biol, Ames, IA 50011 USA Baxter Hemoglobin Therapeut, Boulder, CO 80301 USA Baxter Hemoglobin Therapeut Boulder CO USA 80301 t, Boulder, CO 80301 USA Rice Univ, WM Keck Ctr Computat Biol, Dept Biochem & Cell Biol, Houston, TX 77005 USA Rice Univ Houston TX USA 77005 Biochem & Cell Biol, Houston, TX 77005 USA Univ Nebraska, Dept Biochem, Lincoln, NE 68588 USA Univ Nebraska Lincoln NE USA 68588 a, Dept Biochem, Lincoln, NE 68588 USA Ctr Invest Fijac Nitrogeno, Cuernavaca, Morelos, Mexico Ctr Invest Fijac Nitrogeno Cuernavaca Morelos Mexico ca, Morelos, Mexico
Titolo Testata:
STRUCTURE WITH FOLDING & DESIGN
fascicolo: 9, volume: 8, anno: 2000,
pagine: 1005 - 1014
SICI:
0969-2126(20000915)8:9<1005:CSOANP>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
SPERM WHALE MYOGLOBIN; NITRIC-OXIDE; CARBON-MONOXIDE; LEGHEMOGLOBIN; GENE; FLAVOHEMOGLOBIN; DISSOCIATION; PARASPONIA; RESOLUTION; KINETICS;
Keywords:
anaerobic response; hemoglobin; nonsymbiotic; plant; structure;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Hargrove, MS Iowa State Univ Sci & Technol, Dept Biochem Biophys & Mol Biol, Ames, IA 50011 USA Iowa State Univ Sci & Technol Ames IA USA 50011 IA 50011 USA
Citazione:
M.S. Hargrove et al., "Crystal structure of a nonsymbiotic plant hemoglobin", STRUCT F D, 8(9), 2000, pp. 1005-1014

Abstract

Background: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrationsin a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O-2 conditions. Results: The first X-ray crystal structure of a member of this class of proteins, riceHb1, has been determined to 2.4 Angstrom resolution using a combination of phasing techniques. The active site of ferric riceHb1 differs significantly from those of traditional hemoglobins and myoglobins. The proximal and distal histidine sidechains coordinate directly to the heme iron, forming a hemichrome with spectral properties similar to those of cytochrome b(5). The crystal structure also shows that riceHb1 is a dimer with a novel interface formed by close contacts between the G helix and the region between the B and C helices of the partner subunit. Conclusions: The bis-histidyl heme coordination found in riceHb1 is unusual for a protein that binds O-2 reversibly. However, the distal His73 is rapidly displaced by ferrous ligands, and the overall O-2 affinity is ultra-high (K-D approximate to 1 nM). Our crystallographic model suggests that ligand binding occurs by an upward and outward movement of the E helix, concomitant dissociation of the distal histidine, possible repacking of the CD corner and folding of the D helix. Although the functional relevance of quaternary structure in nsHbs is unclear, the role of two conserved residues in stabilizing the dimer interface has been identified.

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Documento generato il 28/11/20 alle ore 21:49:39