Role of Charge and Hydrophobic Interactions in the Action of Bactericidal/Permeability-increasing Protein of Neutrophils on Gram-negative Bacteria

Abstract

A B S T R A C T

Separation of sublethal and lethal effects of the bactericidal/permeability increasing protein on Escherichia coli.

“…After the indicated incubation at 37°C, aliquots of the bacteria were serially diluted 10,000-fold in sterile isotonic saline containing 4 mM MgCl2 (to prevent further BPI binding [10]) and 400 gg/ml BSA. An aliquot (30 gl) of the diluted sample was transferred to 6 ml of 1.3% (wt/vol) molten (47°C) Bactoagar (Difco Laboratories) containing 0.8% (wt/vol) nutrient broth and 0.5% (wt/vol) NaCl and poured into a Petri dish.…”

“…Remarkably, bacterial growth arrest occurs despite continued macromolecular synthesis for at least 60 min, indicating that initially, BPI causes little gross functional or structural damage (1-5, 7, 8). In fact, addition ofhigh concentrations of divalent cations (Mg2" or Ca2") or trypsin to BPI-treated bacteria removes the bulk of the bound BPI and initiates rapid (15 min) repair ofthe outer envelope damage by active biosynthesis but does not restore bacterial growth (8)(9)(10), further demonstrating the remarkable integrity of BPItreated bacteria.…”

Oxygen-independent intracellular and oxygen-dependent extracellular killing of Escherichia coli S15 by human polymorphonuclear leukocytes.

“…To verify that extracellular E. coli represent noningested rather than previously ingested and extruded bacteria, we examined the bacteria after incubation with PMN to determine whether BPI, a granuleassociated protein, had attached to E. coli. BPI, in crude PMN fractions as well as in purified form, has a high affinity for E. coli (12,17) and rapidly binds to the bacterial surface (18 (Fig. 2).…”

Spontaneous pmrA mutants of Salmonella typhimurium LT2 define a new two-component regulatory system with a possible role in virulence

“…N-terminal amino acids 20 to 44 are responsible for at least part of its bactericidal activity (33). The bactericidal action of CAP57, also referred to as bactericidal permeability-increasing protein, has been extensively studied as well (15,25,40,41,43,44,46,54). As in CAP37, the bactericidal activity resides in the amino-terminal portion of the protein (31).…”