The capability of Yersinia ruckeri to survive in the aquatic systems reflects its adaptation (most importantly through the alteration of membrane permeability) to the unfavorable environments. The nonspecific porins are a key factor contributing to the permeability. Here we studied the influence of the stimuli, such as temperature, osmolarity, and oxygen availability on regulation of Y. ruckeri...

Incubation of mitochondrial outer membrane porin with citraconic anhydride prior to treatment with fluorescein isothiocyanate (FITC) resulted in the labeling of a set of lysines located at a boundary between the water phase and lipid phase. The elution pattern of porin from the cation exchanger has been considered as indicative for the location of lysines. Electrical measurements after reconsti...

Mild trypsin treatment of isolated Neurospora mitochondria strongly inhibits their ability to bind and import the precursors of several mitochondrial proteins. Evidence is presented for two proteins, the ADP/ATP carrier and the mitochondrial porin, that specific binding of the precursors to the outer surface of the mitochondria is affected by the protease treatment. We suggest that the receptor...

In Enterobacteriaceae, the permeability of the outer membrane to hydrophilic antibiotics is associated with the presence of pore-forming proteins. We tested the diffusion of the fluoroquinolone norfloxacin in four Enterobacter cloacae strains: a clinical isolate and three derivatives variously producing or lacking the D and F porins. We analysed the entry of norfloxacin into E. cloacae cells in...

Two major outer membrane proteins of Enterobacter cloacae 206 were purified and identified as porins by using reconstituted vesicles. The 37-kilodalton porin forms a channel with a radius of 0.6 nm, which prefers positively charged substances to negatively charged ones, whereas the 39- to 40-kilodalton porin forms a larger channel with a radius of 0.8 nm, which has weaker selectivity for electr...

Eleven genotypically related Klebsiella pneumoniae isolates were obtained from 11 patients. All isolates were resistant to third-generation cephalosporins due to the production of SHV-2a extended-spectrum beta-lactamase. Comparison of the outer membrane protein profiles revealed one isolate that lacked porins. This porin-deficient isolate was also resistant to cefoxitin (MIC 128 microg ml(-1)) ...

Micromolar concentrations of porin, purified from the outer membranes of Pseudomonas aeruginosa, induced in vitro the classic morphological and biochemical signs of apoptosis in an epithelial cell line (SVC1) derived from the rat seminal vesicle secretory epithelium. The programmed cell death (PCD) was p53 independent and associated with significant decrease of bcl-2 expression, a marked increa...

Native oligomers of three Pseudomonas aeruginosa outer membrane porin proteins and one Escherichia coli porin were demonstrated by using a chemical cross-linking technique. P. aeruginosa protein F, the major constitutive outer membrane porin, was cross-linked to dimers in outer membrane and whole-cell cross-linking experiments. Purified preparations of P. aeruginosa proteins F, D1 (glucose indu...

Involvement of the mitochondrial permeability transition pore (PTP) in apoptosis and PTP structure are highly controversial. In this issue of Molecular Microbiology, experiments based on yeast genetics analyse the roles of the three proteins commonly considered to form the PTP, i.e. porin, ADP/ATP carrier (ACC) and mitochondrial cyclophilin, on apoptosis-like cell death. Whereas knocking out cy...