Functional differentiation of structurally similar membrane subunits of the ABC transporter LolCDE complex

Abstract A photo-sensitive amino acid analogue was introduced into an outer membrane lipoprotein, Pal, and then subjected to photo-crosslinking with the lipoprotein-specific ABC transporter LolCDE. Pal crosslinked to LolE but not LolC in vivo despite that both are structurally similar membrane subunits. LolCDE liganded with Pal containing the photo-sensitive amino acid analogue was isolated and subjected to in vitro photo-crosslinking. LolE was found to be the binding site for Pal. ATP binding to LolD decreased the LolE–Pal crosslinking by decreasing their hydrophobic interaction. ATP hydrolysis in the presence of LolA completely abolished the LolE–Pal crosslinking and, concomitantly, generated a new LolA–Pal crosslinked product. Structured summary of protein interactions LolE and Pal physically interact by cross-linking study ( View interaction ) LolE and Pal bind by cross-linking study ( View interaction ) Pal and Pal bind by cross-linking study ( View interaction ) Pal and LolA physically interact by competition binding ( View interaction )