3.A.1.152.1
LPS export system, LptF (M), LptG (M) and LptB (C).  This system is also listed in TCDB under TC#1.B.42.1.2 as part of a multicomponent system.  The entire system is described in detail there. LptB₂FG extracts LPSs from the IM and transports them to the outer membrane. Luo et al. 2017 reported the crystal structure of nucleotide-free LptB2FG from P. aeruginosa. It shows that LPS transport proteins LptF and LptG each contain a TM domain (TMD), a periplasmic beta-jellyroll-like domain and a coupling helix that interacts with LptB on the cytoplasmic side. The LptF and LptG TMDs form a large outward-facing V-shaped cavity in the IM. Mutational analyses suggested that LPS may enter the central cavity laterally, via the interface of the TMD domains of LptF and LptG, and is expelled into the beta-jellyroll-like domains upon ATP binding and hydrolysis by LptB. These studies suggest a mechanism for LPS extraction by LptB₂FG that is distinct from those of classical ABC transporters that transport substrates across the IM (Luo et al. 2017). LptB2FG extracts LPS from the periplasmic face of the IM through a pair of lateral gates and then powers transperiplasmic transport to the OM through a slide formed by either of the periplasmic domains of LptF or LptG, LptC, LptA and the N-terminal domain of LptD. The structural and functional studies of the seven lipopolysaccharide transport proteins provide a platform to explore the unusual mechanisms of LPS extraction, transport and insertion from the inner membrane to the outer membrane (Dong et al. 2017). LptB2 binds novobiocin which stimulates its export activity and renders the membrane more impermeable to novobiocin (Luo et al. 2017 reported the crystal structure of nucleotide-free LptB2FG from P. aeruginosa. It shows that LPS transport proteins LptF and LptG each contain a TM domain (TMD), a periplasmic beta-jellyroll-like domain and a coupling helix that interacts with LptB on the cytoplasmic side. The LptF and LptG TMDs form a large outward-facing V-shaped cavity in the IM. Mutational analyses suggested that LPS may enter the central cavity laterally, via the interface of the TMD domains of LptF and LptG, and is expelled into the beta-jellyroll-like domains upon ATP binding and hydrolysis by LptB. These studies suggest a mechanism for LPS extraction by LptB₂FG that is distinct from those of classical ABC transporters that transport substrates across the IM (Luo et al. 2017). LptB2FG extracts LPS from the periplasmic face of the IM through a pair of lateral gates and then powers transperiplasmic transport to the OM through a slide formed by either of the periplasmic domains of LptF or LptG, LptC, LptA and the N-terminal domain of LptD. The structural and functional studies of the seven lipopolysaccharide transport proteins provide a platform to explore the unusual mechanisms of LPS extraction, transport and insertion from the inner membrane to the outer membrane (Dong et al. 2017). LptB2 binds novobiocin which stimulates its export activity and renders the membrane more impermeable to novobiocin (Luo et al. 2017). LptB2FG extracts LPS from the periplasmic face of the IM through a pair of lateral gates and then powers transperiplasmic transport to the OM through a slide formed by either of the periplasmic domains of LptF or LptG, LptC, LptA and the N-terminal domain of LptD. The structural and functional studies of the seven lipopolysaccharide transport proteins provide a platform to explore the unusual mechanisms of LPS extraction, transport and insertion from the inner membrane to the outer membrane (Dong et al. 2017). LptB2 binds novobiocin which stimulates its export activity and renders the membrane more impermeable to novobiocin (May et al. 2017).