RESUMEN
The surface of the outer membrane of Gram-negative bacteria is covered by a tightly packed layer of lipopolysaccharide molecules which provide a barrier against many toxic compounds and antibiotics. Lipopolysaccharide, synthesized in the cytoplasm, is assembled in the periplasmic leaflet of the inner membrane where the intermembrane Lpt system mediates its transport to the cell surface. The first step of lipopolysaccharide transport is its extraction from the outer leaflet of inner membrane powered by the atypical LptB2FGC ABC transporter. Here we review latest advances leading to understanding at molecular level how lipopolysaccharide is transported irreversibly to the outer membrane.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Escherichia coli/metabolismo , Lipopolisacáridos/metabolismo , Proteínas de la Membrana Bacteriana Externa/metabolismo , Transporte Biológico/fisiología , Membrana Celular/metabolismo , Conformación ProteicaRESUMEN
Gram-negative bacteria have an outer membrane that is positioned at the frontline of the cell's interaction with the environment and that serves as a barrier against noxious molecules including many antibiotics. This protective function mainly relies on lipopolysaccharide, a complex glycolipid located in the outer leaflet of the outer membrane. In this chapter we will first summarize lipopolysaccharide structure, functions and biosynthetic pathway and then we will discuss how it is transported and assembled to the cell surface. This is a remarkably complex process, as amphipathic lipopolysaccharide molecules must traverse three different cellular compartments to reach their final destination.
Asunto(s)
Membrana Celular/metabolismo , Bacterias Gramnegativas/citología , Bacterias Gramnegativas/metabolismo , Lipopolisacáridos/biosíntesis , Lipopolisacáridos/metabolismo , Transporte BiológicoRESUMEN
Lipopolysaccharides (LPS) are major lipidic components of the outer membrane of most Gram-negative bacteria. They form a permeability barrier that protects these bacteria from harmful compounds in the environment. In addition, they are important signaling molecules for the innate immune system. The mechanism of transport of these molecules to the bacterial cell surface has remained enigmatic for a long time. However, intense research during the last decade, particularly in Escherichia coli and Neisseria meningitidis, has led to the identification of the machinery that mediates LPS transport. In this review, we summarize the current knowledge of the LPS transport machinery and provide an overview of the distribution of the components of this machinery among diverse bacteria, even organisms that don't produce LPS. We also discuss the current insights in the regulation of LPS biosynthesis.