title: 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.
abstract: 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 - DeltaG 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 stabilize the protein. As Plasmodium acyl carrier protein has a similar secondary structure to the other acyl carrier proteins and acyl carrier protein-like domains, the detailed biophysical characterization of Plasmodium acyl carrier protein can serve as a prototype for the analysis of the conformational stability of other acyl carrier proteins.
authors.affiliation: Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Modak
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Sinha
authors.forename: Namita
authors.initials: N
authors.lastname: Surolia
mesh_terms: D000213:Acyl Carrier Protein / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001703:Biophysics / Q000379:methods; D004305:Dose-Response Relationship, Drug; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D010204:Pantetheine / Q000031:analogs & derivatives* / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010963:Plasmodium falciparum / Q000378:metabolism*; D011487:Protein Conformation; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000213:Acyl Carrier Protein; D010455:Peptides; D010204:Pantetheine; C003129:4'-phosphopantetheine