Journal
BIOCHEMISTRY
Volume 40, Issue 41, Pages 12357-12368Publisher
AMER CHEMICAL SOC
DOI: 10.1021/bi010988p
Keywords
-
Categories
Funding
- NIGMS NIH HHS [P01 GM58890] Funding Source: Medline
Ask authors/readers for more resources
A set of variant human hemoglobins, each with an Ala or Gly substitution at a single residue, has been prepared, and the kinetics of their reactions with carbon monoxide have been measured. This reaction is rate-limited by the binding of the first CO to the deoxygenated T state of the protein. The magnitudes of the effects of the mutations on CO combination vary widely, and, with the exception of beta Y145, the residues with the most significant effects on these kinetics are found in the hinge region of the alpha1 beta2 interface. Mixed-metal hybrids, with zinc protoporphyrin IX in place of heme on both alpha or both subunits, were prepared for beta W37E, beta W37A, alpha Y140G, and alpha Y140A, hinge region variants causing large kinetic changes, and for beta Y145G. Such hybrids permit measurements of the kinetics of CO binding to only the heme-containing alpha or beta subunits within the unliganded hemoglobin tetramer. Mutations at beta 37 and alpha 140 have global effects on the T state, increasing the rates of CO binding to both types of subunits. Mutation of beta Y145 has a large effect on the beta subunits in the deoxygenated T state, but very little effect on the (x subunits. Oxygen equilibria measurements on the crystalline T state of beta W37E also indicate large affinity increases in both subunits of this variant. The overall oxygen equilibria of the variant hemoglobins in solution are sensitive to numerous variables besides the properties of the deoxygenated T state. In contrast to CO combination kinetics, the residues whose alterations cause the largest changes in overall oxygen equilibria in solution are scattered seemingly randomly within the alpha1 beta2 interface.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available