Braun's lipoprotein (BLP, Lpp, murein lipoprotein, or major outer membrane lipoprotein), found in some gram-negative cell walls, is one of the most abundant membrane proteins; its molecular weight is about 7.2 kDa. It is bound at its C-terminal end (a lysine) by a covalent bond to the peptidoglycan layer (specifically to diaminopimelic acid molecules[1]) and is embedded in the outer membrane by its hydrophobic head (a cysteine with lipids attached). BLP tightly links the two layers and provides structural integrity to the outer membrane.
| Lipoprotein leucine-zipper | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | LPP | ||||||||
| Pfam | PF04728 | ||||||||
| InterPro | IPR006817 | ||||||||
| CATH | 1jccA00 | ||||||||
| SCOP2 | d1jcca_ / SCOPe / SUPFAM | ||||||||
| |||||||||
| Use IPR016367 for full protein. E. coli protein is P69776. | |||||||||
Characteristics
editThe gene encoding Braun's lipoprotein initially produces a protein composed of 78 amino acids, which includes a 20 amino acid signal peptide at the amino terminus.[2] The mature protein is 6 kDa in size.[3] Three monomers of Lpp assemble into a leucine zipper coiled-coil trimer.[4]
Large amounts of Braun's lipoprotein is present, more than any other protein in E. coli.[5] Unlike other lipoproteins, it is linked covalently to the peptidoglycan.[4] Lpp connects the outer membrane to the peptidoglycan. Lpp is anchored to the outer membrane by its amino-terminal lipid group. In E. coli, one third of Lpp proteins form a peptide bond via the side chain of its carboxy-terminal lysine with diaminopimelic acid in the peptidoglycan layer.[5][6] The rest of the Lpp molecules are present in a "free" form unlinked to peptidoglycan. The free form is exposed on the surface of E. coli.[3]
Functions
editLpp, along with another OmpA-like lipoprotein called Pal/OprL (P0A912), maintains the stability of the cell envelope by attaching the outer membrane to the cell wall.[3]
Lpp has been proposed as a virulence factor of Yersinia pestis, the cause of plague.[7] Y. pestis needs lpp for maximum survival in macrophages and to efficiently kill mouse models of bubonic and pneumonic plague.[8]
Immunology
editBraun's lipoprotein binds to the pattern recognition receptor TLR2. Lpp induces adhesion of neutrophils to human endothelial cells by activating the latter.[9]
References
edit- ^ Seltmann, Guntram; Holst, Otto (2002). The Bacterial Cell Wall. Berlin: Springer. pp. 81–82. ISBN 3-540-42608-6.
- ^ Dramsi S, Magnet S, Davison S, Arthur M (2008). "Covalent attachment of proteins to peptidoglycan". FEMS Microbiology Reviews. 32 (2): 307–20. doi:10.1111/j.1574-6976.2008.00102.x. PMID 18266854.
- ^ a b c Konovalova A, Silhavy TJ (2015). "Outer membrane lipoprotein biogenesis: Lol is not the end". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 370 (1679). doi:10.1098/rstb.2015.0030. PMC 4632606. PMID 26370942.
- ^ a b Kovacs-Simon A, Titball RW, Michell SL (2011). "Lipoproteins of bacterial pathogens". Infection and Immunity. 79 (2): 548–61. doi:10.1128/IAI.00682-10. PMC 3028857. PMID 20974828.
- ^ a b Silhavy TJ, Kahne D, Walker S (2010). "The bacterial cell envelope". Cold Spring Harbor Perspectives in Biology. 2 (5): a000414. doi:10.1101/cshperspect.a000414. PMC 2857177. PMID 20452953.
- ^ Vollmer, Waldemar (2007). "Structure and biosynthesis of the murein (peptidoglycan) sacculus". In Ehrmann, Michael (ed.). The Periplasm ([Online-Ausg.]. ed.). Washington, DC: ASM Press. pp. 198–213. ISBN 9781555813987.
- ^ Butler T (2009). "Plague into the 21st century". Clinical Infectious Diseases. 49 (5): 736–42. doi:10.1086/604718. PMID 19606935.
- ^ Smiley ST (2008). "Immune defense against pneumonic plague". Immunological Reviews. 225: 256–71. doi:10.1111/j.1600-065X.2008.00674.x. PMC 2804960. PMID 18837787.
- ^ McIntyre TM, Prescott SM, Weyrich AS, Zimmerman GA (2003). "Cell-cell interactions: leukocyte-endothelial interactions". Current Opinion in Hematology. 10 (2): 150–8. doi:10.1097/00062752-200303000-00009. PMID 12579042.