Structure of human oxyhaemoglobin at 2.1 A resolution

Area of Science:

• Biochemistry
• Structural Biology
• X-ray Crystallography

Background:

• Human haemoglobin transports oxygen, with its structure crucial for function.
• Understanding oxyhaemoglobin's precise atomic arrangement is key to elucidating oxygen transport mechanisms.

Purpose of the Study:

• To determine the high-resolution three-dimensional structure of human oxyhaemoglobin.
• To analyze the structural differences between alpha and beta subunits and their active sites.
• To investigate the role of terminal residues in the allosteric mechanism.

Main Methods:

• Single crystal X-ray diffraction analysis at 2.1 A resolution.
• Data collection using an Arndt-Wonacott camera at -2°C.
• Structure refinement using the Jack-Levitt method.

Main Results:

• Detailed atomic coordinates and bond lengths of oxyhaemoglobin were determined.
• Distinct structural features were observed in the alpha and beta subunit active sites, including haem planarity and hydrogen bonding.
• C-terminal residues were found to be delocalized, differing from their deoxyhaemoglobin conformation, suggesting a modified role in allostery.

Conclusions:

• The quaternary structure of oxyhaemoglobin is similar to carbon monoxide haemoglobin.
• Structural findings support existing allosteric models for oxygen binding.
• The role of penultimate tyrosine residues in the allosteric mechanism may require re-evaluation.