Studies on the Chemistry of Hemoglobin
Year: 1967
Type: article
Abstract: This paper presents a model for the reaction of hemoglobin with ligands on the basis of the evidence that the αβ dimer is the unit of structure and function in the molecule and that there are very strong interactions between the α and β chains in a dimer. Thus, for all practical purposes, it can be assumed that 2 molecules of ligand combine with the αβ dimer at one time. The model is developed to show that there are five types of molecules in solutions of partially saturated hemoglobin: nonliganded tetramers, α2β2; liganded tetramers, α2*β2*; hybrid molecules composed of one liganded and one nonliganded dimer, αβα*β*; liganded dimers, α*β*; and nonliganded dimers, αβ. The contribution of these various species of hemoglobin to the total solute concentration clearly depends on the values of the tetramer to dimer dissociation constants for the liganded, nonliganded, and hybrid tetramers. The existence of hybrid molecules of the type αβα*β* is a key event in the combination of hemoglobin with ligand, because the affinity for ligand of the nonliganded dimer in such a hybrid molecule is assumed to differ from that of a dimer in a nonliganded tetramer. The model is expressed in quantitative terms, and it is shown that the derived equations describe the experimentally obtained oxygen saturation curves. Furthermore, the persistence of a high value of the Hill interaction coefficient, n, in solutions which promote the dissociation of the hemoglobin tetramers, α2β2, into αβ dimers (the so-called paradox of strong salt solutions) is compatible with the model proposed, which in fact predicts that this state of affairs will occur.
Source: Journal of Biological Chemistry
Author: Guido Guidotti
Institution: Harvard University
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1532270203