High resolution crystal structures of the deoxy, oxy, and aquomet forms of cobalt myoglobin

Eric Allen Brucker, John S. Olson, George N. Phillips, Yi Dou, Masao Ikeda-Saito

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


The structures of the deoxy, oxy, and aquomet forms of native sperm whale myoglobin reconstituted with cobalt protoporphyrin IX have been determined by x-ray crystallography. As expected, cobalt myoglobin closely resembles native iron myoglobin in overall structure, especially in their respective aquomet forms. In the cobalt oxymyoglobin structure, the N(ε) of distal histidine 64 lies within hydrogen bonding distance to both the oxygen atom directly bonded to the cobalt and the terminal oxygen atom, in agreement with previous EPR and resonance Raman studies. The metal atom in cobaltous myoglobin does show a small 0.06-Å out-of-porphyrin plane displacement when moving from the oxy to deoxy state. In the case of the native iron-containing myoglobin, the oxy to deoxy transition results in a larger 0.16-Å displacement of the metal farther out of the porphyrin plane, attributed to an increase in spin from S = 0 to S = 2. The small displacement in cobalt myoglobin is due to a change in coordination geometry, not spin state (S = 1/2 for both cobalt deoxy- and oxymyoglobin). The small out-of-porphyrin plane movement of cobalt which accompanies deoxygenation of myoglobin also occurs in cobalt hemoglobin and serves to explain why cooperativity, although reduced, is still preserved when iron is replaced by cobalt in human hemoglobin.

Original languageEnglish
Pages (from-to)25419-25422
Number of pages4
JournalJournal of Biological Chemistry
Issue number41
Publication statusPublished - 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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