Demonstration of inositol hexaphosphate induced changes in structure at ligand binding sites in carp hemoglobin carbonyl
Onwubiko, H.A.; Hazzard, J.H.; Noble, R.W.; Caughey, W.S.
Biochemical and Biophysical Research Communications 106(1): 223-228
1982
ISSN/ISBN: 0006-291X PMID: 7103982 Document Number: 190743
IR and 13C-NMR spectra for carbonyl ligands bound to Hb from carp, Cyprinus carpio, at pH 6.0 and 25.degree. C underwent marked shifts when inositol hexaphosphate (IHP) was added to the solution. The relative intensities of the 2 C-O stretch bands at 1951 and 1968 cm-1 due to 2 ligand site conformers were altered by IHP in the same manner as found upon lowering the pH in the absence of IHP. Both the lowering of pH and the binding of IHP enhanced the 1968 cm-1 band conformer, the confomrer normally of much lower stability. 13C-NMR spectra indicated the CO sites for only 1 type of subunit, probably the .beta.-subunit, are altered by IHP. The observed IHP-induced shift from high affinity (R) to a low affinity (T) form is accompanied by a significant change in ligand binding site structure at 2 of the 4 subunits.