Bacterial outer membrane
Lipopolysaccharide-assembly, LptC-related | |||||||||
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Identifiers | |||||||||
Symbol | LptC | ||||||||
Pfam | PF06835 | ||||||||
Pfam clan | CL0259 | ||||||||
InterPro | IPR010664 | ||||||||
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Lipopolysaccharide-assembly | |||||||||
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Identifiers | |||||||||
Symbol | LptE | ||||||||
TCDB | 1.B.42 | ||||||||
OPM superfamily | 412 | ||||||||
OPM protein | 4q35 | ||||||||
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The bacterial outer membrane is found in gram-negative bacteria. Gram-negative bacteria form two lipid bilayers in their cell envelopes - an inner membrane (IM) that encapsulates the cytoplasm, and an outer membrane (OM) that encapsulates the periplasm.[1]
The composition of the outer membrane is distinct from that of the inner
Porins can be found in this layer.[2]
Outer membrane proteins
Outer membrane proteins are membrane proteins with key roles associated with bacterial cell structure and morphology; cell membrane homeostasis; the uptake of nutrients; protection of the cell from toxins including antibiotics; and virulence factors including adhesins, exotoxins, and biofilm formation.[3][4] There are a number of outer membrane proteins that are specifically virulence-related.
Outer membrane proteins consist of two major classes of protein - transmembrane proteins and lipoproteins. The transmembrane proteins form channels or pores in the membrane called porins, and actively pumping efflux channels.[5]
The outer membranes of a bacterium can contain a huge number of proteins. In E. Coli for example there are around 500,000 in the membrane.[5]
Bacterial outer membrane proteins typically have a unique beta barrel structure that spans the membrane. The beta barrels fold to expose a hydrophobic surface before their insertion into the outer membrane. Beta barrels vary in sequence and size that ranges from 8 to 36 beta strands. A subset of OMPs have a perisplasmic or an extracellular link to their beta barrel structure. [3] An outer membrane protein is translocated across the inner membrane through ‘’Sec’’ machinery, and finally inserted to the outer membrane by the barrel assembly machinery complex.
Biogenesis
The
The
LptC is required for the translocation of lipopolysaccharide (LPS) from the inner membrane to the outer membrane.[12] LptE forms a complex with LptD, which is involved in the assembly of LPS in the outer leaflet of the outer membrane and is essential for envelope biogenesis.[12][13][14]
Clinical significance
If
See also
- Host–pathogen interaction
- OMPdb
- Outer membrane efflux proteins
- Outer mitochondrial membrane