Mechanism and energetics of dipeptide transport in membrane vesicles of Lactococcus lactis.

摘要: Alanyl-alpha-glutamate transport has been studied in Lactococcus lactis ML3 cells and membrane vesicles fused with liposomes containing beefheart cytochrome c oxidase as a proton-motive-force-generating system. The uptake of Ala-Glu observed de-energized can be stimulated 26-fold upon addition lactose. No intracellular dipeptide pool could detected intact cells. In membranes, 40-fold accumulation was response to proton motive force. Addition ionophores uncouplers resulted rapid efflux the accumulated dipeptide, indicating that is directly coupled force driving an electrogenic process transported symport two protons. both membranes same affinity constant (0.70 mM) for found. Accumulated exchangeable externally added alanyl-glutamate, glutamyl-glutamate, leucyl-leucine, while no exchange occurred amino acid glutamate or alanine. These results indicate system broad substrate specificity.