Xyloside transport by XylP, a member of the galactoside-pentoside-hexuronide family

This paper describes the functional characterization of the xyloside transporter, XylP, of Lactobacillus pentosus with the aid of a spectroscopy-based assay system. In or-der to monitor the transport reaction, the natural xylo-side isoprimeverose, a building block of hemicellulose, and the analogue methyl-isoprimeverose were chemically synthesized by a new and efficient procedure. The XylP protein was purified by metal affinity chromatography, following high level expression in Lactococcus lactis from the nisin-inducible promoter. The purified XylP protein was incorporated into liposomes, in which the glucose dehydrogenase from Acinetobacter calcoaceticus (sGDH) was entrapped. sGDH can oxidize aldose sugars in the presence of dichlorophenol-indophenol as electron accep-tor. The coupled assay thus involves XylP-mediate