Michael Waterman
Faculty Member
Last active: 2/12/2015

Effect of carbamidomethylation of cysteine residues G11(104)alpha on the properties of hemoglobin A.

Waterman MR
Biochim Biophys Acta. 1976 439 (1): 167-74

PMID: 182235 · DOI:10.1016/0005-2795(76)90173-2

A modified hemoglobin tetramer has been prepared containing carbamidomethylated G11(104)alpha cysteine residues. The molecule is electrophoretically identical to hemoglobin A, at pH 8.6, contains 2 titratable sulfhydryl groups per tetramer, and shows a normal oxygen affinity at half-saturation. However, the cooperative oxygen binding is significantly decreased. As the G11(104)alpha cysteine residues are located at the alpha1beta1 contact point in the hemoglobin tetramer, the results of this study indicate that modification within this portion of the molecule does not interfere with the assembly of subunits to form a tetramer or the resultant p50 but can cause a significant alteration of cooperative oxygen binding. In addition, spin-labels attached to this cysteine residue are not sensitive to changes in conformation which may take place at this contact point during oxygen binding. It is therefore possible that modification of the G11(104)alpha cysteine residue abolishes the contribution of the alpha1beta1 contact point to the cooperative oxygen binding phenomenon.

MeSH Terms (12)

Binding Sites Cysteine Electron Spin Resonance Spectroscopy Electrophoresis, Disc Hemoglobins Humans Iodoacetamide Macromolecular Substances Oxygen Oxyhemoglobins Protein Binding Protein Conformation

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