Cationic Proteins of Polymorphonuclear Leukocyte Lysosomes II. Composition, Properties, and Mechanism of Antibacterial Action

ZEYA, H.I.(University ofNorthCarolina, Chapel Hill), ANDJ.K.SPITZNAGEL. Cationic proteins ofpolymorphonuclear leukocyte lysosomes. II.Composition, properties, andmechanism ofantibacterial action. J.Bacteriol. 91:755-762. 1966.A basic proteins fraction fromguinea pigpolymorphonuclear (PMN)granules was obtained byacidextraction andprecipitation with20%(v/v) ethyl alcohol. The fraction accounted formostoftheantibacterial activity ofthePMN granules and corresponded totheantibacterial cationic components ofintact granules (bands I, II,andIII) resolved byzoneelectrophoresis. Absence fromthefraction ofcomponents identical totheenzymatic components ofintact lysosomes showed that the fraction wasessentially free fromlysosomal enzymes. Theaminoacidanalysis of proteins inthefraction gaveapreponderance ofbasic aminoacids (25%),especially ofarginine (16%). Thecomparative aminoacid analysis showed that thelysosomal cationic proteins (LCP)fraction wasmarkedly different fromnuclear histones. The LCPfraction manifested antibacterial activity against certain gram-negative and gram-positive microorganisms, including Candida albicans, andexhibited stoichiometric relationship inits activity. Microorganisms treated withLCPfraction were agglutinated. Anionic substances suchasnucleic acids, heparin, andendotoxin effectively blocked theantibacterial activity ofthefraction. TheLCPfraction caused suppression ofoxygen uptake bybacterial cells anddamaged thepermeability barriers ofcells asmanifested byrapid release ofP32aswell asultraviolet-absorbing material at260m,u, inthesupernatant fluid. Thepreceding paper dealt withtheelectrophoretic resolution oftheantibacterial activity of polymorphonuclear (PMN)lysosomes, distinct fromknownlysosomal enzymes. Theactivity was associated withcationic protein components which migrated fastest towards thecathode ahead oflysozyme andother enzymes. Thispaper describes someofthebiological and biochemical properties ofthelysosomal cationic proteins inrelation tothemechanism oftheir antibacterial activity.