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'''THE STRUCTURE OF ASCARIS HEMOGLOBIN DOMAIN I AT 2.2 ANGSTROMS RESOLUTION: MOLECULAR FEATURES OF OXYGEN AVIDITY''' | '''THE STRUCTURE OF ASCARIS HEMOGLOBIN DOMAIN I AT 2.2 ANGSTROMS RESOLUTION: MOLECULAR FEATURES OF OXYGEN AVIDITY''' | ||
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[[Category: Mathews, F S.]] | [[Category: Mathews, F S.]] | ||
[[Category: Yang, J.]] | [[Category: Yang, J.]] | ||
[[Category: | [[Category: Oxygen storage]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 10:38:53 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 07:38, 2 May 2008
THE STRUCTURE OF ASCARIS HEMOGLOBIN DOMAIN I AT 2.2 ANGSTROMS RESOLUTION: MOLECULAR FEATURES OF OXYGEN AVIDITY
Overview
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.
About this Structure
1ASH is a Single protein structure of sequence from Ascaris suum. Full crystallographic information is available from OCA.
Reference
The structure of Ascaris hemoglobin domain I at 2.2 A resolution: molecular features of oxygen avidity., Yang J, Kloek AP, Goldberg DE, Mathews FS, Proc Natl Acad Sci U S A. 1995 May 9;92(10):4224-8. PMID:7753786 Page seeded by OCA on Fri May 2 10:38:53 2008
