@entity1 granulocytes express a 55-kDa XXXX on the cell surface that is identical to the bactericidal/permeability-increasing protein.

@entity1 @entity5752 @entity3275 @entity19499 @entity5038 @entity5750 @entity26181 @entity2823 @entity7965 @entity214
Several LPS-binding proteins have been identified on the surface of @entity1 granulocytes (polymorphonuclear leukocyte (PMN)). We describe a plasma-membrane associated ca. 55-kDa @entity5752 of @entity1 PMN that is indistinguishable from the bactericidal/permeability-increasing protein ( @entity19499 ). To detect LPS-binding proteins on the cell surface, PMN were biotinylated before detergent solubilization and incubation with LPS-coated beads. Several biotinylated proteins bound to LPS-coated beads but not to uncoated beads and were characterized after elution with detergent by @entity214 -PAGE and western blotting using streptavidin-horseradish peroxidase. The spectrum of biotinylated proteins binding to and eluting from LPS-coated beads increased as the number of beads incubated with PMN lysate increased. However, at all concentrations of beads a 55-kDa protein was a dominant component of the eluate. Binding of the 55-kDa protein to LPS-coated beads was inhibited by @entity3275 , and both homologous and heterologous LPS, but not by peptidoglycan. Similar amounts of biotinylated 55-kDa @entity5752 were detected on PMN from @entity1 with @entity7965 who lacked membrane bound @entity5750 , a known ca. 55-kDa plasma membrane-associated @entity5752 , indicating that the recovered biotinylated protein is not @entity5750 . Several pieces of evidence, however, do indicate that the 55-kDa surface protein is @entity19499 : 1) flow cytometry of PMN after labeling with rabbit anti- @entity19499 serum and @entity2823 -labeled goat anti-rabbit IgG revealed immunoreactive surface molecules on resting PMN and, in increased amounts, on PMN stimulated with @entity5038 or TNF; 2) This antiserum specifically and quantitatively inhibited binding of the biotinylated 55-kDa species to LPS-coated beads; 3) both @entity19499 and the 55-kDa protein migrated as a doublet during @entity214 -PAGE and were both converted to single migrated species after N-glycosidase F treatment; 4) chemical cleavage of the biotinylated protein and native @entity19499 with @entity26181 yielded the same fragments. Thus, we have positively identified @entity19499 as a @entity5752 on the surface of PMN. The role of this potent antibacterial, endotoxin neutralizing protein on the surface of PMN remains to be established.
