outermembrankomponent

Outermembrankomponent is a term used in cell biology to describe the proteins and lipids that compose the outer membrane of certain cells and organelles. It is most commonly applied to the outer membrane of Gram-negative bacteria, but analogous structures exist in mitochondria and chloroplasts of eukaryotes.

The outer membrane contains a variety of components. Beta-barrel outer membrane proteins (OMPs), including porins, form channels that allow selective passage of small molecules. Lipoproteins anchored in the membrane contribute structural stability and signaling roles. In Gram-negative bacteria, lipopolysaccharide (LPS) resides in the outer leaflet and contributes to the permeability barrier and immune recognition. In mitochondria, outer membrane components include voltage-dependent anion channels (VDACs) and related porins that regulate metabolite exchange.

Biogenesis and assembly of outer membrane components involve specialized pathways. In bacteria, most OMPs are exported across the inner membrane via the Sec or Tat systems, folded in the periplasm, and inserted into the outer membrane by the β-barrel assembly machinery (Bam complex). LPS and other lipids are trafficked to the outer membrane by distinct transport systems, such as the Lpt pathway.

Functions of outermembrankomponent include establishing a selective permeability barrier, mediating nutrient uptake and waste efflux, and participating in host–pathogen interactions. Variations in outer membrane composition can influence antibiotic susceptibility and virulence. The term also encompasses structures like outer membrane vesicles, which shed these components for communication and transfer.

See also: porins, VDAC, Bam complex, Lpt pathway, outer membrane vesicles.