1ASH

THE STRUCTURE OF ASCARIS HEMOGLOBIN DOMAIN I AT 2.2 ANGSTROMS RESOLUTION: MOLECULAR FEATURES OF OXYGEN AVIDITY

Summary for 1ASH

• Entry DOI: 10.2210/pdb1ash/pdb
• Descriptor: HEMOGLOBIN (OXY), PROTOPORPHYRIN IX CONTAINING FE, OXYGEN MOLECULE, ... (4 entities in total)
• Functional Keywords: oxygen storage
• Biological source: Ascaris suum (pig roundworm)
• Cellular location: Secreted, extracellular space: P28316
• Total number of polymer chains: 1
• Total formula weight: 18618.69

Authors

Yang, J.,Mathews, F.S.,Kloek, A.P.,Goldberg, D.E. (deposition date: 1995-01-06, release date: 1995-02-27, Last modification date: 2024-02-07)

Primary citation

Yang, J.,Kloek, A.P.,Goldberg, D.E.,Mathews, F.S.
The structure of Ascaris hemoglobin domain I at 2.2 A resolution: molecular features of oxygen avidity.
Proc.Natl.Acad.Sci.USA, 92:4224-4228, 1995

PubMed 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 A 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 A 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.

PubMed: 7753786
DOI: 10.1073/pnas.92.10.4224

Experimental method

X-RAY DIFFRACTION (2.15 Å)