Title: CO-binding studies on Hb M Iwate Allostery of a T state haemoglobin
Abstract: The mutant haemoglobin Hb M Iwate, α2Mmet87His→Tyrβ2, is characterized by a stable T structure and a low ligand affinity. Sigmoidal CO-binding isotherms of symmetrical shape with Hill coefficients of n = 1.4 at pH 6 to n = 1.9 at pH 10 and the differences in the mean affinity (pCO(12)) and the affinity of the first ligand-binding β subunit (1/L1 > pCO(12) are the evidence for the cooperativity. The comparison of the Bohr effects of the two valency hybrid states (α2Mmetβmetβdeoxyα2Mmetβ2deoxy) in the absence of and in the presence of polyphosphates leads to an indirect proof of pH-dependent subunit-subunit interaction. Inositol hexaphosphate-binding suppresses cooperativity in the pH range 5.5–8 (n = 1). Above pH 8 the cooperativity increases to a final value of n = 1.9 at pH > 10, which is identical to that of stripped Hb M Iwate. The CO binding to the first binding site exhibits a Bohr effect. Polyphosphate anions have no influence on the CO binding of the first binding site. The heterotropic effects are discussed as intrachain effects (Bohr effect of the first binding site) and interchain effects (Bohr effect of pCO(12); influence of polyphosphates).
Publication Year: 1979
Publication Date: 1979-11-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 1
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot