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Transition of haemoglobin between two tertiary conformations: Inositol hexakisphosphate increases the transition constant and the affinity of sheep haemoglobin for 5,5′-dithiobis(2-nitrobenzoate)

Okonjo, K. O. and Adeogun, I. A. and Babalola, J. O, (2008) Transition of haemoglobin between two tertiary conformations: Inositol hexakisphosphate increases the transition constant and the affinity of sheep haemoglobin for 5,5′-dithiobis(2-nitrobenzoate). Biochimica et Biophysica Acta, 1794. pp. 398-409.

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Abstract

The equilibrium constant (Kequ) for the reaction of 5,5′-dithiobis(2-nitrobenzoate) — DTNB — with the CysF9 [93]β sulphydryl group of the haemoglobins of the sheep decreases by about two orders of magnitude between pH≈5.6 and 9.2: from a mean of 7.2±1 to a mean of 0.044±0.01. Calculations from the pH dependence of Kequ show that in the r⇌t tertiary conformational transition of haemoglobin the t isomer population is 50.7 and 61.8% for the major and minor haemoglobins, respectively. In the presence of inositol hexakisphosphate (inositol-P6), Kequ increases for both haemoglobins by about an order of magnitude through most of the pH range. The t isomer population also increases to 82.1 and 79.6% for the major and minor haemoglobins, respectively. These results indicate that inositol-P6 increases the affinity of the sulphydryl for DTNB by increasing the population of the t isomer. It is highly probable that a minimum fourstate model that includes the r⇌t transition is required for a full understanding of haemoglobin function.

Item Type: Article
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Engineering, Science and Mathematics > School of Chemistry
Depositing User: Mr Adewole Adewumi
Date Deposited: 04 Jul 2011 18:44
Last Modified: 13 Dec 2011 21:13
URI: http://eprints.covenantuniversity.edu.ng/id/eprint/397

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