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

Nitric oxide induced conformational changes in opossum hemoglobin.

John ME, Waterman MR
J Biol Chem. 1979 254 (23): 11953-7

PMID: 40988

Opossum hemoglobin assumes a T quaternary structure upon NO ligation in the absence of organic phophates at pH 6.7. In addition, stripped opossum hemoglobin exhibits a low oxygen affinity when compared to human hemoglobin and a pH-dependent heme-heme interaction with an n value of 2.14 at pH 7.0 and 2.46 at pH 7.35. These observations indicate that opossum hemoglobin may have a destabilized oxy structure when compared to hemoglobin A due to differences in primary structure. Thus, the strong trans ligand effect of nitric oxide is able to disrupt the proximal histidine-iron bond in the alpha-hemes triggering a conformational transition to the T state. Absence of a distal histidine in the alpha-subunits and, therefore an impaired donor acceptor interaction with the sixth ligand, could contribute to the lack of stability of the R quaternary structure in opossum nitrosylhemoglobin. The reduced oxygen affinity of opossum hemoglobin may be compensated for by other physiological factors such as a reduced phosphate effect.

MeSH Terms (14)

Amino Acids Animals Electron Spin Resonance Spectroscopy Hemoglobin A Hemoglobins Humans Hydrogen-Ion Concentration Kinetics Nitric Oxide Opossums Oxyhemoglobins Protein Binding Protein Conformation Species Specificity

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