Evidence for association of lipopolysaccharide with Pseudomonas fluorescens strain MF0 porin OprF

Lipopolysaccharide (LPS) was found to be associated with the major outer me mbrane protein OprF of the psychrotrophic bacterium Pseudomonas fluorescens MFO, using two OprF purification procedures. OprF, purified under mild con ditions, presented two types of association with LPS: tight (tLPS) and slig ht (sLPS), both of type R. LPS protected OprF from heat modification and tr ypsin degradation and facilitated the reincorporation of purified OprF into an artificial lipid bilayer without affecting its pore-forming activity. T he size of the OprF channel depended on cell, growth temperature, as did th e extent of LPS phosphorylation: we suggest that LPS may be involved in mod ifications of OprF pore formation. (C) 2000 Editions scientifiques et medic ales Elsevier SAS.