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1ash

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(New page: 200px<br /> <applet load="1ash" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ash, resolution 2.15&Aring;" /> '''THE STRUCTURE OF AS...)
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Revision as of 10:51, 8 November 2007

Image:1ash.gif

1ash, resolution 2.15Å

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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 with HEM and OXY as ligands. 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

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