Proton nuclear magnetic resonance studies of hemoglobin providence (β82EF6 Lys → Asn or Asp): a residue involved in anion binding

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Abstract
High-resolution proton NMR studies of [human] Hb Providence-Asn (.beta.82EF6 Lys .fwdarw. Asn) and Providence-Asp (.beta.82EF6 Lys .fwdarw. Asp) show that different amino acid substitutions at the same position in the Hb molecule have different effects on the structure of the protein molecule. Hb Providence-Asp appears to be in a low-affinity tertiary structure in the deoxy and carbonmonoxy forms. Deoxyhemoglobin Providence-Asn has its .beta. heme resonance shifted downfield slightly from its position in normal adult Hb; however, the teritary structures of the heme pocket of Hb A and Hb Providence-Asn are very similar when both proteins are in the carbonmonoxy form. These results are consistent with the oxygen equilibrium measurements of Bonaventura, J., et al. which show that Hb Providence-Asn and Hb Providence-Asp have oxygen affinities lower than normal adult Hb, with Hb Providence-Asp having the lowest. Studies on the effects of sodium chloride on the hyperfine shifted proton resonances of deoxyhemoglobins A, Providence-Asn, and Providence-Asp indicate that the .beta.82EF6 lysine is probably 1, but not the only binding site for chloride ions.