Voltage‐dependent cationic channels formed by a cytolytic toxin produced by Gardnerella vaginalis

Abstract

A eytotytis toxin gr~duecd by C, vrr#innli.r WBX incorporated in ~rrislsirl membrnnrs and giant lipotemca. The taxin t'otmed ionic &arm& when incr)rpQrrrrd in lipid bilryera. 7% elce~ricrl properties er such channels were rludicd. Currcnr rccordn rcw~ltd 11 unitary eondurlunec of I 26 pS (in x~mmctricsl ISO mM KCI), The @en ntuls prebirbility of the cy~al&n formed rhennclw wax n Bune~lan of the Lpplicd membrane patcnrial.The permeability ratia alMans to ~nionx wxx estimated IQ bc 6.5, I INTROBUCTIONGarcim=@lla Ya&inah is an apporruniatie QathOgen, which is closely associated with bacterial vaginitis [1,2]$ A cytolytic toxin (CTOX) produced by G. vnginalis has been rcccnrIy described [3], This toxin is an amphiphilic protein with a molecular mass of 61-43 kDa [3], The CTOX has r? lyric activity towards human crythrocytes and nucleated cells, such as human endothelial cells and

Physical characterization of the pore forming cytolysine from Gardnerella vaginalis

“…It implies that the pore formed by CTox has a diameter between these two values, in agreement with Kretzschmar et al [12]. This range fits well with the conductance of 125 pS and with the Ca 2÷permeability found in the electrophysiological measurements of CTox-formed pores in lipid membranes [7]. As described before, the lytic activity of CTox is not coupled with direct phospholipase activity [5].…”

“…The presence of ionic channels on the membrane of giant liposomes containing CTox has been revealed in a previous work [7], using the patch-clamp technique. A highly homogeneous cationic (PK/Po = 6.5) conductance population, of 125 Jr 4 pS was recorded.…”

“…CTox does not have a direct lytic enzymatic activity as phospholipase [5], and the evidence of its ability to form ionic channels in lipid membranes [7], suggests the hypothesis of pore formation as the mechanism underlying cell lysis. Furthermore, the particular characteristics of the CTox-formed channels in lipid membranes, such as electric conductance, cationic selectivity and voltage dependence, prompted us to confirm these findings and design experiments where the hemolytic effect of CTox was analyzed.…”

“…The finding of voltage-activated cationic channels in proteoliposomes containing CTox suggested the hypothesis that the toxin forms a transmembrane pore [7]. Here, we attempted to correlate the electrophysiological properties of CTox and its cytolytic activity on human erythrocytes.…”

Gardnerella vaginalis: characteristics, clinical considerations, and controversies

“…The value found by the thermal denaturation midpoint method was 42 mol% (234). The cesium chloride buoyant density gradient centrifugation method gave values of 43.1 (82) Investigations have been limited by difficulties experienced in lysing G. vaginalis (80,82,174 (150) studied the electrical properties of ionic channels formed upon introduction of the cytolytic toxin into artificial membranes. The successful incorporation into liposomes indicated that the channel-forming conformation of the protein is independent of the erythrocyte target specificity of the cytotoxin.…”