In molecular biology, the lipid-binding serum glycoproteins family, also known as the BPI/LBP/Plunc family or LBP/BPI/CETP family represents a family which includes mammalianlipid-binding serumglycoproteins and/or proteins containing a structural motif known as the BPI fold. Members of this family include:
These proteins consist of N- and C-terminaldomains, which share a similar two-layer alpha/beta structure, but show little sequence identity to each other. These domains were first described as being arranged in a "boomerang" shape that creates the BPI fold.[4] The fold contains apolar binding pockets that can interact with hydrophobic and amphipathic molecules, such as the acyl carbon chains of lipopolysaccharide found on Gram-negative bacteria.
Lipopolysaccharide-binding protein (LBP) is an endotoxin-binding protein that is closely related to, and functions in a co-ordinated manner with BPI to facilitate an integrated host response to invading Gram-negative bacteria.[7]
Palate, lung and nasal epithelium carcinoma-associated protein (PLUNC) is a potential host defensive protein that is secreted from the submucosal gland to the saliva and nasal lavage fluid. PLUNC appears to be a secreted product of neutrophil granules that participates in an aspect of the inflammatory response that contributes to host defence.[10]
Short palate, lung and nasal epithelium clone 1 (SPLUNC1) may bind the lipopolysaccharide of Gram-negative nanobacteria, thereby playing an important role in the host defence of nasopharyngealepithelium.[11]
Bacterial permeability family member A1 (BPIFA1/SPLUNC1) is an innate protein that is secreted basolaterally from healthy, but not asthmatic, human bronchial epithelial cultures (HBECs). It suppresses airway smooth muscle contractility by binding to and inhibiting the Ca2+ influx channel Orai1.[12]
^Beamer LJ, Carroll SF, Eisenberg D (June 1997). "Crystal structure of human BPI and two bound phospholipids at 2.4 angstrom resolution". Science. 276 (5320): 1861–4. doi:10.1126/science.276.5320.1861. PMID9188532.
^Kleiger G, Beamer LJ, Grothe R, Mallick P, Eisenberg D (June 2000). "The 1.7 A crystal structure of BPI: a study of how two dissimilar amino acid sequences can adopt the same fold". J. Mol. Biol. 299 (4): 1019–34. doi:10.1006/jmbi.2000.3805. PMID10843855. S2CID2392067.
^Weiss J (August 2003). "Bactericidal/permeability-increasing protein (BPI) and lipopolysaccharide-binding protein (LBP): structure, function and regulation in host defence against Gram-negative bacteria". Biochem. Soc. Trans. 31 (Pt 4): 785–90. doi:10.1042/bst0310785. PMID12887306. S2CID1155741.
^Hamilton JA, Deckelbaum RJ (February 2007). "Crystal structure of CETP: new hopes for raising HDL to decrease risk of cardiovascular disease?". Nat. Struct. Mol. Biol. 14 (2): 95–7. doi:10.1038/nsmb0207-95. PMID17277799. S2CID22193394.
^Ponsin G, Qu SJ, Fan HZ, Pownall HJ (April 2003). "Structural and functional determinants of human plasma phospholipid transfer protein activity as revealed by site-directed mutagenesis of charged amino acids". Biochemistry. 42 (15): 4444–51. doi:10.1021/bi027006g. PMID12693940.
^Zhou HD, Li GY, Yang YX, Li XL, Sheng SR, Zhang WL, Zhao J (April 2006). "Intracellular co-localization of SPLUNC1 protein with nanobacteria in nasopharyngeal carcinoma epithelia HNE1 cells depended on the bactericidal permeability increasing protein domain". Mol. Immunol. 43 (11): 1864–71. doi:10.1016/j.molimm.2005.10.021. PMID16364440.