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Biochemical and Functional Characterization of a Membrane-associated Pore-forming Protein from the Pathogenic Ameboflagellate Naegleria fowleri

Authors :
John Ding-E Young
D M Lowrey
Source :
Journal of Biological Chemistry. 264:1077-1083
Publication Year :
1989
Publisher :
Elsevier BV, 1989.

Abstract

A membrane-bound cytolytic pore-forming protein (N-PFP) produced by the pathogenic ameboflagellate Naegleria fowleri was characterized. N-PFP was solubilized from ameba membranes by detergent and enriched 300-fold by gel filtration chromatography. When analyzed by gel electrophoresis, N-PFP migrates with a molecular mass of 66 kDa and 50-54 kDa, under reducing and non-reducing conditions, respectively. In addition to lysing erythrocytes, N-PFP is cytotoxic to several tumor cell lines tested. Its hemolytic activity is not dependent on the presence of divalent cations. N-PFP rapidly depolarizes the membrane potential of microelectrode-impaled chicken embryo myocytes, suggesting that functional channel formation may represent the mode of membrane damage. In planar bilayers, N-PFP forms ion channels with heterogeneous unit conductances ranging between 150 and 400 picosiemens in 0.1 M NaCl and that are relatively resistant to closing by high voltages. Upon heat treatment (75 degrees C, 30 min), N-PFP forms channels with unit conductances that are on average larger than those formed by untreated N-PFP. N-PFP channels are slightly more permeable to cations than to anions. Using a liposome swelling-shrinkage assay, the functional diameter of N-PFP channels is estimated to range between 3.6 and 5.2 nm. N-PFP is immunologically distinct from the PFP/perforin produced by lymphocytes, the terminal components of complement and a PFP from the ameba Entamoeba histolytica, all of which produce pores on target membranes. This protein may have a direct lytic role during target cell killing mediated by N. fowleri.

Details

ISSN :
00219258
Volume :
264
Database :
OpenAIRE
Journal :
Journal of Biological Chemistry
Accession number :
edsair.doi...........2bc67d57302660920fec67c74dc5245e
Full Text :
https://doi.org/10.1016/s0021-9258(19)85056-1