Very high resolution structure of a trematode hemoglobin displaying a TyrB10-TyrE7 heme distal residue pair and high oxygen affinity

Alessandra Pesce, Sylvia Dewilde, Laurent Kiger, Mario Milani, Paolo Ascenzi, Michael C. Marden, Marie Louise Van Hauwaert, Jacques Vanfleteren, Luc Moens, Martino Bolognesi

Research output: Contribution to journalArticlepeer-review

Abstract

Monomeric hemoglobin from the trematode Paramphistomum epiclitum displays very high oxygen affinity (P50 <0.001 mm Hg) and an unusual heme distal site containing tyrosyl residues at the B10 and E7 positions. The crystal structure of aquo-met P. epiclitum hemoglobin, solved at 1.17 Å resolution via multiwavelength anomalous dispersion techniques (R-factor = 0.121), shows that the heme distal site pocket residue TyrB10 is engaged in hydrogen bonding to the iron-bound ligand. By contrast, residue TyrE7 is unexpectedly locked next to the CD globin region, in a conformation unsuitable for heme-bound ligand stabilisation. Such structural organization of the E7 distal residue differs strikingly from that observed in the nematode Ascaris suum hemoglobin (bearing TyrB10 and GlnE7 residues), which also displays very high oxygen affinity. The oxygenation and carbonylation parameters of wild-type P. epiclitum Hb as well as of single- and double-site mutants, with residue substitutions at positions B10, E7 and E11, have been determined and are discussed here in the light of the protein atomic resolution crystal structure.

Original languageEnglish
Pages (from-to)1153-1164
Number of pages12
JournalJournal of Molecular Biology
Volume309
Issue number5
DOIs
Publication statusPublished - Jun 22 2001

Keywords

  • Heme distal residues
  • Hemoglobin
  • Hemoproteins
  • Trematode hemoglobin
  • Very high resolution protein structure

ASJC Scopus subject areas

  • Virology

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