Kinetics of carbon monoxide binding to Fe(TPP)(Im) and Fe(TPP)(Im-): evidence regarding protein control of heme reactivity Academic Article uri icon


  • Protein structure modulation of the reactivity of a heme prosthetic group has been a focus for numerous investigations. 1 For example, ligand binding kinetics of hemoglobin are affected by protein conformation. 1a,2 The CO on-rate for the low-affinity T state is ~20-60-fold less than that for the high-affinity R state. 3 One plausible mechanism of this modulation has been advanced by Peisach and collaborators. 4 It is generally proposed that a protein can induce changes in heme reactivity through structural changes at the proximal imidazole. For hemoglobin, in the low-affinity state the proximal histidine is thought to be in its neutral form with a proton on N-1. The high-affinity form is considered to have a strong hydrogen bond to that proton, which in the limit might be thought of as corresponding to a deprotonated imidazole as the sixth ligand. Such a mechanism also has been invoked to discuss the electronic structure of cytochromes c from different organisms, 5 and the crystal structures of a number of hemoproteins. 6 . © 1979, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Swartz, J. C., Stanford, M. A., Moy, J. N., Hoffman, B. M., & Valentine, J. S

citation count

  • 34

complete list of authors

  • Swartz, James C||Stanford, Marlene A||Moy, James N||Hoffman, Brian M||Valentine, Joan S

publication date

  • June 1979