The structure of Ascaris hemoglobin domain I at 2.2 Å resolution: Molecular features of oxygen avidity

J. Yang, A. P. Kloek, D. E. Goldberg, F. S. Mathews

Research output: Contribution to journalArticle

127 Scopus citations

Abstract

The perienteric hemoglobin of the parasitic nematode Ascaris has an exceptionally high affinity for oxygen. It is an octameric protein containing two similar heme-binding domains per subunit, but recombinant constructs expressing a single, monomeric heme-binding domain (domain 1; D1) retain full oxygen avidity. We have solved the crystal structure of D1 at 2.2 Å resolution. Analysis of the structure reveals a characteristic globin fold and illuminates molecular features involved in oxygen avidity of Ascaris perienteric hemoglobin. A strong hydrogen bond between tyrosine at position 10 in the B helix (tyrosine-B10) and the distal oxygen of the ligand, combined with a weak hydrogen bond between glutamine-E7 and the proximal oxygen, grips the ligand in the binding pocket. A third hydrogen bond between these two amino acids appears to stabilize the structure. The B helix of D1 is displaced laterally by 2.5 Å when compared with sperm whale myoglobin. This shifts the tyrosine-B10 hydroxyl far enough from liganded oxygen to form a strong hydrogen bond without steric hindrance. Changes in the F helix compared with myoglobin contribute to a tilted heme that may also be important for oxygen affinity.

Original languageEnglish
Pages (from-to)4224-4228
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume92
Issue number10
DOIs
StatePublished - Jan 1 1995

Keywords

  • oxygen binding
  • protoporphyrin IX
  • x-ray crystallography

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