4IRO image
Entry Detail
PDB ID:
4IRO
Title:
Crystal structure of T-state carbonmonoxy hemoglobin from Trematomus bernacchii at pH 8.4
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2013-01-15
Release Date:
2013-02-20
Method Details:
Experimental Method:
Resolution:
2.20 Å
R-Value Work:
0.21
R-Value Observed:
0.22
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Hemoglobin subunit alpha
Chain IDs:A, C
Chain Length:143
Number of Molecules:2
Biological Source:Trematomus bernacchii
Polymer Type:polypeptide(L)
Description:Hemoglobin subunit beta
Chain IDs:B, D
Chain Length:146
Number of Molecules:2
Biological Source:Trematomus bernacchii
Primary Citation
Role of tertiary structures on the Root effect in fish hemoglobins.
Biochim.Biophys.Acta 1834 1885 1893 (2013)
PMID: 23376186 DOI: 10.1016/j.bbapap.2013.01.031

Abstact

Many fish hemoglobins exhibit a marked dependence of oxygen affinity and cooperativity on proton concentration, called Root effect. Both tertiary and quaternary effects have been evoked to explain the allosteric regulation brought about by protons in fish hemoglobins. However, no general rules have emerged so far. We carried out a complementary crystallographic and microspectroscopic characterization of ligand binding to crystals of deoxy-hemoglobin from the Antarctic fish Trematomus bernacchii (HbTb) at pH6.2 and pH8.4. At low pH ligation has negligible structural effects, correlating with low affinity and absence of cooperativity in oxygen binding. At high pH, ligation causes significant changes at the tertiary structural level, while preserving structural markers of the T state. These changes mainly consist in a marked displacement of the position of the switch region CD corner towards an R-like position. The functional data on T-state crystals validate the relevance of the crystallographic observations, revealing that, differently from mammalian Hbs, in HbTb a significant degree of cooperativity in oxygen binding is due to tertiary conformational changes, in the absence of the T-R quaternary transition. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.

Legend

Protein

Chemical

Disease

Primary Citation of related structures