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Tertiary conformational transition in sheep hemoglobins induced by reaction with 5,5´-dithiobis(2-nitrobenzoate) and by binding of inositol hexakisphosphate

Okonjo, K. O. and Adeogun, I. A. and Babalola, J. O, (2009) Tertiary conformational transition in sheep hemoglobins induced by reaction with 5,5´-dithiobis(2-nitrobenzoate) and by binding of inositol hexakisphosphate. Biophysical Chemistry. pp. 65-75.

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Abstract

We have determined the second-order reverse rate constant, kR, for the reaction of 5,5´-dithiobis(2- nitrobenzoate) – DTNB – with sheep hemoglobins as a function of pH from values of the second-order forward rate constant, kF, and the equilibrium constant, Kequ, at 25 °C: kR¼ kF Kequ. We demonstrate that (i) inositol hexakisphosphate (inositol-P6) decreases kF and kR by increasing Krt, the r⇌t tertiary conformation transition constant; (ii) the conformation favored for both the forward and reverse reactions is the r conformation. For stripped hemoglobin we obtain from the kF data a t isomer population of 34.6% (±14) prior to reaction with DTNB; from the kR data we calculate a t isomer population of 44.8% (±4) following reaction with DTNB. In the presence of inositol-P6 the latter value is increased to 79.5% (±2). These results demonstrate that an allosteric transition occurs on reaction with DTNB and on inositol-P6 binding.

Item Type: Article
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Engineering, Science and Mathematics > School of Chemistry
Depositing User: Mr Kehinde Adetiloye
Date Deposited: 30 Jun 2011 23:33
Last Modified: 13 Dec 2011 21:13
URI: http://eprints.covenantuniversity.edu.ng/id/eprint/356

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