Interaction of porin from Yersinia pseudotuberculosis with different structural forms of endogenous lipopolysaccharide.
The interaction of Yersinia pseudotuberculosis porin solubilized 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.
Vakorina
T I
TI
Pacific Institute of Bioorganic Chemistry, Far East Branch of the Russian Academy of Sciences, Vladivostok 690022, Russia. vakorina@piboc.dvo.ru
Novikova
O D
OD
Krasikova
I N
IN
Naberezhnykh
G N
GN
Solov'eva
T F
TF
Ovodov
Yu S
YS
D008070:Lipopolysaccharides / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D018272:Porins / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D015011:Yersinia pseudotuberculosis / Q000378:metabolism*
D008070:Lipopolysaccharides; D018272:Porins