Molecular characterization of the plasmid-encoded lactose-PTS of Lactobacillus casei

The lactose-P'TS was first described in Staphylococcus aureus [1-2]. The system was demonstrated to be composed of three components: (1) an integral 55 kDa membrane protein, Enzymell!"; responsible for the vectorial phosphorylation and translocation of lactose into the cell as lactose 6-phosphate [3], (2) FactorIII1ac, a 39 kDa trimeric peripheral membrane protein that ph osphorylates Enzymell!" [4], and (3) the soluble 54 kDa lactose 6-phosphate-hydrolyzing enzyme, P,B-gal [5]. The overall reaction catalyzed by the lactose-PTS may be written as: