Purification and characterization of pertucin produced by Pseudomonas pertucinogena

Pertucin, a bacteriocin active against phase I organisms of Bordetella pertussis, was extracted from Pseudomonas pertucinogena, strain 190 or 6627, by freezing and thawing of bacteria-free agar medium and was purified by ammonium sulfate fractionation, dialysis, zinc chloride precipitation, and polyacrylamide gel electrophoresis. The specific activity of purified pertucin was approximately 80 times that of the crude extract. The purified pertucin preparation was homogeneous on ultracentrifugal analysis and polyacrylamide gel electrophoresis, and was found to be composed of protein (80%) and carbohydrate (20%), the latter assumed not to be bound covalently to the protein. Neither nucleic acids nor lipids were demonstrated. N-terminal analysis by dansylation revealed only methionine in strain 190 and only glycine in strain 6627. The isoelectric point was found to be 4.8, and the molecular weight was estimated to be 31,500. Amino acid analysis of the protein moiety demonstrated that it contained all of the common amino acids with somewhat more of the hydrophilic amino acids. With respect to thermostability, pH stability, and effects of metal ions and various buffers, pertucin behaves like a protein and is stable in 0.05 M tris(hydroxymethyl)aminomethane buffer, pH 8.0, containing 0.01 M Ca(2+).