title: Stability and dynamics of the porcine odorant-binding protein.
abstract: The denaturation process of porcine odorant-binding protein (pOBP) was studied by intrinsic fluorescence analysis and far- and near-UV circular dichroism measurements. Our results showed that a reversible one-step process described the denaturation by GdnHCl. The midpoint of the transition, that is, the point where the free energies of protein in the native and unfolded states are equal, corresponds to 2.3 M GdnHCl. The difference in free energy between native and unfolded states of pOBP is -5.95 kcal/mol in the absence of GdnHCl, indicating that the protein molecule is very stable to the denaturing action of GdnHCl. A 15% increase in fluorescence intensity accompanied by a 25% decrease of fluorescence decay lifetime recorded in the range of 0.0-1.4 M GdnHCl was explained by the destruction of the complex between Trp 16 and the positively charged atom NZ of Lys 120, localized over the center of the Trp 16 indole ring, with concurrent formation of complex between Trp 16 and bound water molecules also located in its close vicinity.
authors.affiliation: Institute of Protein Biochemistry, CNR, Naples, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Staiano
authors.forename: Sabato
authors.initials: S
authors.lastname: D'Auria
authors.forename: Antonio
authors.initials: A
authors.lastname: Varriale
authors.forename: Mose'
authors.initials: M
authors.lastname: Rossi
authors.forename: Anna
authors.initials: A
authors.lastname: Marabotti
authors.forename: Carlo
authors.initials: C
authors.lastname: Fini
authors.forename: Olesya V
authors.initials: OV
authors.lastname: Stepanenko
authors.forename: Irina M
authors.initials: IM
authors.lastname: Kuznetsova
authors.forename: Konstantin K
authors.initials: KK
authors.lastname: Turoverov
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D019791:Guanidine / Q000494:pharmacology; D011489:Protein Denaturation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D018035:Receptors, Odorant / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013552:Swine; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry
chemical_list: D018035:Receptors, Odorant; C045648:odorant-binding protein; D014364:Tryptophan; D019791:Guanidine