Effects of pH on structural and functional properties of porin from the outer membrane of Yersinia pseudotuberculosis. II. Characterization of pH-induced conformational intermediates of yersinin

• Published in: Biochemistry (Moscow). Supplement series A, Membrane and cell biology Membrane and cell biology, 2007-06, Vol.1 (2), p.154-162
• Main Authors: Novikova, O. D., Kim, N. Yu, Luk’yanov, P. A., Likhatskaya, G. N., Emel’yanenko, V. I., Solov’eva, T. F.
• Format: Article
• Language: English
• Subjects: Circular dichroism; Dichroism; Fluorescent indicators; Intermediates; Membranes; Monomers; pH effects; Protein folding; Protein structure; Proteins; Pseudotuberculosis; Secondary structure; Spectroscopy; Structure-function relationships; Titration; Trimers; Yersinia pseudotuberculosis
• ISSN: 1990-7478; 1990-7494
• DOI: 10.1134/S1990747807020080

pH-Induced intermediates of Omp F-like porin from the outer membrane of Yersinia pseudotuberculosis (yersinin) were characterized by fluorescence and fluorescent probe spectroscopy and circular dichroism. The most dramatic changes in the intrinsic fluorescence of the protein induced by pH titration correlated with different conformational states of the porin molecule. pH-induced conformational transitions of yersinin can be described in terms of a three-state model: (1) disordering of porin associates and formation of porin trimers structurally similar to the native protein; (2) unfolding of individual porin domains followed by cooperative dissociation of trimers into monomers; (3) formation of two loosely structured forms of monomer intermediates. It is assumed that one of these monomeric forms (at pH 3.0) corresponds to the molten-globule state of porin with native secondary structure, while the other one (at 2.0) represents a partly denatured (misfolded) monomer, which retains no more than 50% of the regular secondary structure. The putative mechanism of low pH-induced β-barrel unfolding is discussed in terms of a theoretical model of yersinin spatial structure.