Modulation of oxygen binding to insect hemoglobins: The structure of hemoglobin from the botfly Gasterophilus intestinalis

Alessandra Pesce, Marco Nardini, Sylvia Dewilde, David Hoogewijs, Paolo Ascenzi, Luc Moens, Martino Bolognesi

Research output: Contribution to journalArticle

Abstract

Hemoglobins (Hbs) reversibly bind gaseous diatomic ligands (e.g., O 2) as the sixth heme axial ligand of the penta-coordinate deoxygenated form. Selected members of the Hb superfamily, however, display a functionally relevant hexa-coordinate heme Fe atom in their deoxygenated state. Endogenous heme hexa-coordination is generally provided in these Hbs by the E7 residue (often His), which thus modulates accessibility to the heme distal pocket and reactivity of the heme toward exogenous ligands. Such a pivotal role of the E7 residue is prominently shown by analysis of the functional and structural properties of insect Hbs. Here, we report the 2.6 Å crystal structure of oxygenated Gasterophilus intestinalis Hb1, a Hb known to display a penta-coordinate heme in the deoxygenated form. The structure is analyzed in comparison with those of Drosophila melanogaster Hb, exhibiting a hexa-coordinate heme in its deoxygenated derivative, and of Chironomus thummi thummi HbIII, which displays a penta-coordinate heme in the deoxygenated form. Despite evident structural differences in the heme distal pockets, the distinct molecular mechanisms regulating O2 binding to the three insect Hbs result in similar O2 affinities (P50 values ranging between 0.12 torr and 0.46 torr). Published by Cold Spring Harbor Laboratory Press.

Original languageEnglish
Pages (from-to)3057-3063
Number of pages7
JournalProtein Science
Volume14
Issue number12
DOIs
Publication statusPublished - Dec 2005

Keywords

  • Gasterophilus intestinalis hemoglobin
  • Heme hexa-/penta-coordination
  • Insect hemoglobin
  • Oxygen recognition
  • Parasitic botfly hemoglobin
  • Protein structure

ASJC Scopus subject areas

  • Biochemistry

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