Location of the Higher Affinity Copper Site on Human Hemoglobin by the Use of the Spin Label Technique

摘要

Addition of copper (II) ions to Cys beta -93 maleimide spin-labelled human hemoglobin A produces a dramatic decrease in the amplitude of the spin-label ESR spectra. This effect was analyzed in the framework of Leigh's theory which permits interspin distances to be deduced from the effect of dipolar coupling on the ESR spectra and led to an estimate of 9A as the distance between the label and the higher affinity copper site. Taking into account the previous results which suggest that four nitrogen atoms coordinate with copper, and that the N terminal val beta -1 and His beta -2 residues are involved, the location of the higher affinity copper site is proposed to be at the beta sub 1 beta sub 2 interface of the hemoglobin molecule, involving the N terminal of one beta subunit and the C terminal of the other. (Atomindex citation 16:026692)