Structure and Ligand Selection of Hemoglobin II from Lucina pectinata

Lucina pectinata ctenidia harbor three heme proteins: sulfide-reactive hemoglobin I (HbILp) and the oxygen transporting hemoglobins II and III (HbIILp and HbIIILp) that remain unaffected by the presence of H2S. The mechanisms used by these three proteins for their function, including ligand control,...

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Published in:The Journal of biological chemistry 2008-04, Vol.283 (14), p.9414-9423
Main Authors: Gavira, José A., Camara-Artigas, Ana, De Jesús-Bonilla, Walleska, López-Garriga, Juan, Lewis, Ariel, Pietri, Ruth, Yeh, Syun-Ru, Cadilla, Carmen L., García-Ruiz, Juan Manuel
Format: Article
Language:English
Subjects:
Animals
Bivalvia - chemistry
Bivalvia - metabolism
Crystallography, X-Ray
Dimerization
Heme - chemistry
Heme - metabolism
Hemoglobins - chemistry
Hemoglobins - metabolism
Hydrogen Bonding
Lucina pectinata
Oxygen - chemistry
Oxygen - metabolism
Protein Structure and Folding
Spectrum Analysis, Raman
Structural Homology, Protein
Sulfites - chemistry
Sulfites - metabolism
Water - chemistry
Water - metabolism
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Summary:Lucina pectinata ctenidia harbor three heme proteins: sulfide-reactive hemoglobin I (HbILp) and the oxygen transporting hemoglobins II and III (HbIILp and HbIIILp) that remain unaffected by the presence of H2S. The mechanisms used by these three proteins for their function, including ligand control, remain unknown. The crystal structure of oxygen-bound HbIILp shows a dimeric oxyHbIILp where oxygen is tightly anchored to the heme through hydrogen bonds with Tyr30(B10) and Gln65(E7). The heme group is buried farther within HbIILp than in HbILp. The proximal His97(F8) is hydrogen bonded to a water molecule, which interacts electrostatically with a propionate group, resulting in a Fe-His vibration at 211 cm-1. The combined effects of the HbIILp small heme pocket, the hydrogen bonding network, the His97 trans-effect, and the orientation of the oxygen molecule confer stability to the oxy-HbIILp complex. Oxidation of HbILp Phe(B10) → Tyr and HbIILp only occurs when the pH is decreased from pH 7.5 to 5.0. Structural and resonance Raman spectroscopy studies suggest that HbIILp oxygen binding and transport to the host bacteria may be regulated by the dynamic displacements of the Gln65(E7) and Tyr30(B10) pair toward the heme to protect it from changes in the heme oxidation state from FeII to FeIII.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M705026200