Biomaterial Database

Analysis of the order of free energy couplings between ligand binding and subunit assembly in human hemoglobin. 1986

M L Johnson

The concept of free energy couplings has been extensively used in studies of the ligand-linked subunit assembly of oligomeric proteins such as human hemoglobin A [cf. Ackers, G. K. (1980) Biophys. J. 32, 331-346]. Recently, the concept of "order" of free energy couplings has been introduced as a description of the number of protein subunits that must be liganded to effect changes in intersubunit interactions [Weber, G. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7098-7102]. That report utilized the concept of order of free energy couplings to analyze a set of previously published equilibrium constants derived from data pertaining to the chemical equilibrium between oxygen and stripped hemoglobin A [Mills, F. C., Johnson, M. L., & Ackers, G. K. (1976) Biochemistry 15, 5350-5362]. The Weber report claims to have "unequivocally" demonstrated that the coupling between oxygenation and subunit assembly in hemoglobin A is "first order". In the present report, it is demonstrated that free energy couplings of both the first and second order are capable of describing the original oxygen binding data.

UI	MeSH Term	Description	Entries
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D006441	Hemoglobin A	Normal adult human hemoglobin. The globin moiety consists of two alpha and two beta chains.
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular