title: Distinct steps in the penetration of adenylate cyclase toxin of Bordetella pertussis into sheep erythrocytes. Translocation of the toxin across the membrane.
abstract: Adenylate cyclase (AC) toxin from Bordetella pertussis penetrates eukaryotic cells and upon activation by calmodulin generates unregulated levels of intracellular cAMP. The process of toxin penetration into sheep erythrocytes was resolved into three consecutive steps including insertion, translocation, and intracellular cleavage. Insertion of the toxin into the cell membrane occurred over a wide temperature range (4-36 degrees C). In contrast, translocation of the toxin, i.e. transfer of the NH2-terminal catalytically active fragment across the membrane, occurred only above 20 degrees C and was highly temperature-dependent. While a single exposure of the toxin to Ca2+ was sufficient for its insertion into the plasma membrane, toxin translocation required exogenous Ca2+ at mM concentrations. Translocation was not affected by pretreatment of cells with trypsin, N-ethylmaleimide, and sodium carbonate at alkaline pH. The NH2-terminal fragment of the toxin was cleaved in the cell releasing the 45-kDa active AC into the cytosol. The cleavage was blocked by treatment of cells with N-ethylmaleimide. It is hypothesized that the COOH-terminal portion of the toxin creates in the membrane a channel through which the NH2-terminal fragment is translocated.
authors.affiliation: Department of Clinical Microbiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Rogel
authors.forename: E
authors.initials: E
authors.lastname: Hanski
mesh_terms: D037361:Adenylate Cyclase Toxin; D000818:Animals; D001692:Biological Transport; D001886:Bordetella pertussis / Q000472:pathogenicity*; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D008970:Molecular Weight; D012756:Sheep; D013329:Structure-Activity Relationship; D013696:Temperature; D010566:Virulence Factors, Bordetella / Q000737:chemistry / Q000378:metabolism*
chemical_list: D037361:Adenylate Cyclase Toxin; D010566:Virulence Factors, Bordetella; D010450:Endopeptidases; D005033:Ethylmaleimide; D002118:Calcium