Interaction of Porin from Yersinia pseudotuberculosis with Different Structural Forms of Endogenous Lipopolysaccharide

T. I. Vakorina^1*, O. D. Novikova¹, I. N. Krasikova¹, G. N. Naberezhnykh¹, T. F. Solov'eva¹, and Yu. S. Ovodov²

¹Pacific Institute of Bioorganic Chemistry, Far East Branch of the Russian Academy of Sciences, pr. 100-letiya Vladivostoka 159, Vladivostok 690022, Russia; fax: 7 (4232) 31-4050; E-mail: vakorina@piboc.dvo.ru

²Institute of Physiology, Komi Science Center, Urals Branch of the Russian Academy of Sciences, ul. Pervomaiskaya 50, Syktyvkar 167982, Russia; fax: (8212) 24-1001; E-mail: ovoys@physiol.komisc.ru

^* To whom correspondence should be addressed.

Received December 17, 2002; Revision received July 21, 2003

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The interaction of Yersinia pseudotuberculosis porinsolubilized in deoxycholate with the S- and R-forms of endogenous lipopolysaccharide (LPS) was studied by the quenching of intrinsic protein fluorescence. The samples of S-LPS differed both in the length of O-specific polysaccharide (n = 1 and 4) and in the acylation degree of the 3-hydroxytetradecanoic acid residues of the lipid A moiety (12-66%). R-LPS (12%) binding to porin was found to occur with positive cooperativity on two integrated structural regions of the R-LPS macromolecule, namely, core oligosaccharide and lipid A. The mode of porin interaction with low-acylated S-LPSs (15 or 20%) coincided with a model involving three types of binding sites. The shape of Scatchard curves of binding indicates that a complex formation between porin and low-acylated S-LPS is cooperative at low and moderate ligand concentration, whereas at near-saturating LPS concentrations porin binds to LPS independently on two types of binding sites. The O-specific polysaccharide chain in the S-LPS macromolecule increases the affinity of its interaction with porin in comparison with R-LPS-porin binding. A significant increase (to 66%) in the degree of S-LPS acylation substantially changed its porin-binding character: the process became anti-cooperative with lowered affinity. Thus, the features of LPS-porin interaction significantly depend on the conformational changes in the LPS molecule due to expanding of its hydrophobic region.

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KEY WORDS: Yersinia pseudotuberculosis, outer membrane, lipopolysaccharide, porin, lipopolysaccharide-protein interaction, protein fluorescence

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