Zur Wirkung von Liganden auf das Assoziations‐Dissoziations‐Gleichgewicht des Methämoglobins der Flußneunaugen (Lampetra fluviatilis L.)

Abstract

The dissociation-association equilibrium of lamprey methemoglobin as a function of protein concentration, pH, and ligandation of the heme Fe3+ has been studied using sedimentation analysis.The sedimentation constant s ;~,~ of MetHb in the pH range 4.5 < pH < 10 amounts to 1.94 S leading to a calculated molecular weight of 17000 which corresponds to the Hb protomer.At pH 7.5 the MetHb * N, complex is monomeric. Below pH 5.7 and a t high protein concentration the dimer of 34000, s ;~,~ = 3.13 S, is formed, the dimerization being accompanied by an uptake of two protons per protomer : (a) (1)

Convergent evolution of hemoglobin switching in jawed and jawless vertebrates

“…The agnathan Hb (aHb) is structurally distinct from the gnathostome Hb, although it carries out similar functions. aHb is a monomer in its oxygenated form and associates into homodimers or tetramers when deoxygenated [ 21 , 22 ]. Like the gnathostome Hbs, aHbs display cooperative O 2 binding and a pH-dependent regulation of O 2 affinity [ 23 ].…”

Lamprey Hemoglobin

“…Behlke and Scheler (8) showed with sedimentation velocity measurements that ligated Hb from a similar species of lamprey (Lampetra fluviatilis) also self-associates, but only at low pH. Although the metHb was found to be monomeric, addition of metHb ligands such as azide or cyanide causes dimer formation at low pH (9). This property, oxidationinduced dissociation and ligand-dependent reassociation, absent in other vertebrate Hbs, but found in the Hbs of organisms of five invertebrate phyla, is another indication of the functional relationship of lamprey and invertebrate Hbs (10).…”