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Báo cáo khoa học: Isothermal unfolding studies on the apo and holo forms of Plasmodium falciparum acyl carrier protein Role of the 4¢-phosphopantetheine group in the stability of the holo form of Plasmodium falciparum acyl carrier protein

The unfolding pathways of the two forms ofPlasmodium falciparumacyl carrier protein, the apo and holo forms, were determined by guanidine hydrochloride-induced denaturation. Both the apo form and the holo form displayed a reversible two-state unfolding mechanism. The analysis of iso-thermal denaturation data provides values for the conformational stability of the two proteins. | ỊFEBS Journal Isothermal unfolding studies on the apo and holo forms of Plasmodium falciparum acyl carrier protein Role of the 4 -phosphopantetheine group in the stability of the holo form of Plasmodium falciparum acyl carrier protein Rahul Modak1 Sharmistha Sinha2 and Namita Surolia1 1 Molecular Biology and Genetics Unit JawaharlalNehru Centre for Advanced Scientific Research Jakkur Bangalore India 2 Molecular Biophysics Unit Indian Institute of Science Bangalore India Keywords apo-ACP conformationalstability holo-ACP isothermal unfolding 4 -phosphopantetheine Correspondence N. Surolia Molecular Biology and Genetics Unit JawaharlalNehru Centre for Advanced Scientific Research Jakkur Bangalore 560064 India Fax 91 80 22082766 Tel 91 80 2208282021 E-mail surolia@jncasr.ac.in Received 29 January 2007 revised 15 April 2007 accepted 1 May 2007 doi 10.1111 j.1742-4658.2007.05856.x The unfolding pathways of the two forms of Plasmodium falciparum acyl carrier protein the apo and holo forms were determined by guanidine hydrochloride-induced denaturation. Both the apo form and the holo form displayed a reversible two-state unfolding mechanism. The analysis of isothermal denaturation data provides values for the conformational stability of the two proteins. Although both forms have the same amino acid sequence and they have similar secondary structures it was found that the - DG of unfolding of the holo form was lower than that of the apo form at all the temperatures at which the experiments were done. The higher stability of the holo form can be attributed to the number of favorable contacts that the 4 -phosphopantetheine group makes with the surface residues by virtue of a number of hydrogen bonds. Furthermore there are several hydrophobic interactions with 4 -phosphopantetheine that firmly maintain the structure of the holo form. We show here for the first time that the interactions between 4 -phosphopantetheine and the polypeptide backbone of acyl carrier protein .