Characterization of the lactose-specific enzymes of the phosphotransferase system in Lactococcus lactis.

摘要: The plasmid-encoded lactose genes of the Lactococcus lactis phosphotransferase system encoding Enzyme IIIlac (lacF) and IIlac (lacE) have been identified cloned in Escherichia coli L. lactis. Nucleotide sequence transcription analysis showed that these are organized into a lactose-inducible operon with gene order lacF-lacE-lacG-lacX, latter two phospho-beta-galactosidase 34-kDa protein an unknown function, respectively. lac-operon is immediately followed by IS element homologous to ISS1. was purified from determination its NH2-terminal demonstrated lacF starts TTG codon encodes 105 amino acid (Mr = 11416). Cross-linking studies enzyme active as trimer. A mutant strain YP2-5 appeared encode containing missense mutation G18E. could be expressed under control vector-located promoter sequences resulting overproduction E. complementation YP2-5. deduced consists 586 acids 61562) shows characteristics hydrophobic, integral membrane protein. primary structures those Staphylococcus aureus (72 71% identity, respectively) Lactobacillus casei (48 47% respectively). In contrast, organization differs significantly between Gram-positive bacteria. Heterogramic homology specific domains observed derived lactose-specific enzymes IIIcel IIcel, which suggest common function transport phosphorylation structurally related beta-glucosides.