Opposite Effects of Lysophosphatidylethanolamines on Conformation of OmpF-like Porin from Yersinia pseudotuberculosis.

Lysophosphatidyletnolamine (LPE) is one of enigmatic lipids of bacteria. It is generated from major membrane lipid - phosphatidylethanolamine at severe changes of the bacterial growth conditions. Accumulation of this phospholipid in cells of Gram-negative enterobacterium Yersinia pseudotuberculosis results in the enhanced thermostability of OmpF-like porin (YOmpF) from the same bacteria. The respective integral conformational rearrangements may disturb the channel permeability of protein under stress conditions. However, role of fatty acid composition of LPE in this effect remained unclear. Present work demonstrated that the level of unsaturated LPE is 3.5 times higher than saturated one in total LPE of bacterial cells exposed to stress (phenol treatment). Unsaturated 1-oleoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (MOPE) and saturated LPE 1-palmitoyl-2- hydroxy-sn-glycero-3-phosphoethanolamine (MPPE) oppositely affect the conformation of YOmpF. MOPE increases the protein thermal stability due to more dense packing of monomers in porin and preserves its trimeric form at elevated temperature, while MPPE weakens the contact between monomers and promotes dissociation of the protein.

Tubular immunostimulating complex based on cucumarioside A2-2 and monogalactosyldiacylglycerol from marine macrophytes.

BACKGROUND: There is an urgent need to develop safe and effective adjuvants for the new generation of subunit vaccines. We developed the tubular immunostimulating complex (TI-complex) as a new nanoparticulate antigen delivery system. The morphology and composition of TI-complexes principally differ from the known vesicular immunostimulating complexes (ISCOMs). However, methodology for the preparation of TI-complexes has suffered a number of shortcomings. The aim of the present work was to obtain an antigen carrier consisting of triterpene glycosides from Cucumaria japonica, cholesterol, and monogalactosyldiacylglycerol from marine macrophytes with reproducible properties and high adjuvant activity. RESULTS: The cucumarioside A2-2 - cholesterol - MGalDG ratio of 6:2:4 (by weight) was found to provide the most effective formation of TI-complexes and the minimum hemolytic activity in vitro. Tubules of TI-complexes have an outer diameter of about 16 nm, an inner diameter of 6 nm, and a length of 500 nm. A significant dilution by the buffer gradually destroyed the tubular nanoparticles. The TI-complex was able to increase the immunogenicity of the protein antigens from Yersinia pseudotuberculosis by three to four times. CONCLUSIONS: We propose an optimized methodology for the preparation of homogeneous TI-complexes containing only tubular particles, which would achieve reproducible immunization results. We suggest that the elaborated TI-complexes apply as a universal delivery system for different subunit antigens within anti-infectious vaccines and enhance their economic efficacy and safety.