Purification and partial amino acid sequence of plantaricin 1.25 alpha and1.25 beta, two bacteriocins produced by Lactobacillus plantarum TMW1.25

Two bacteriocins produced by Lactobacillus plantarum TMW1.25 have been puri fied by a four-step purification procedure, including ammonium sulphate pre cipitation and cation-exchange chromatography followed by hydrophobic-inter action chromatography on octyl sepharose. The final purification was perfor med by repeated reversed-phase chromatography steps which yielded two bacte riocin fractions designated plantaricin 1.25 alpha and plantaricin 1.25 bet a. The molecular masses of the peptides in these fractions were 5979 and 52 03 Da, respectively. Combination of the fractions did not have any synergis tic effects on bacteriocin activity, indicating that they each contain a on e-peptide bacteriocin. The major peptide in the alpha fraction was blocked at its N-terminus, and a partial sequence (25 residues) could only be obtai ned after cleavage with CNBr. This sequence did not show clear homologies w ith known bacteriocins. The beta peptide has been sequenced almost complete ly and consists, presumably, of 53 residues. This peptide displayed strong homology to the known N-terminal part of brevicin 27 produced by Lactobacil lus brevis SB27. The results showed that the beta peptide contains as many as six consecutive lysine residues at the N-terminus.