Structure of deoxy-quaternary haemoglobin with liganded beta subunits.
We have determined the structure of a T-state haemoglobin in which the haem groups of the beta subunits have carbon monoxide bound, and the alpha subunits have nickel replacing the haem iron and are ligand-free. The structural adjustments on binding ligand in the T state are in the same direction as those associated with the quaternary transition, and a translational shift of the haem is severely restricted. We explain how these observations may account for the low ligand affinity of the beta haem of T-state haemoglobin.
Luisi
B
B
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Liddington
B
B
Fermi
G
G
Shibayama
N
N
D000494:Allosteric Regulation; D006418:Heme; D006454:Hemoglobins / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D014961:X-Ray Diffraction
D006454:Hemoglobins; D008024:Ligands; D006418:Heme