title: Cold-labile hemolysin produced by limited proteolysis of theta-toxin from Clostridium perfringens.
abstract: A nicked toxin whose hemolytic activity is temperature dependent was obtained by limited proteolysis of theta-toxin (Mr 54,000) with subtilisin. The nicked toxin (C theta) is a complex of two fragments: the N-terminal fragment (Mr 15,000) with basic isoelectric point and the C-terminal fragment (Mr 39,000) with the single cysteinyl residue of the toxin whose reduced form is essential for the hemolytic activity. C theta hemolyzes erythrocytes only at temperatures above 25 degrees C, whereas the native toxin hemolyzes them even at 10 degrees C. At temperatures below 25 degrees C, C theta does not hemolyze them although it does bind to membrane cholesterol and although no distinct difference was observed between the secondary structure of C theta and that of native toxin. It was found that C theta binds to the cells only in a reversible manner at low temperature, while the native one binds irreversibly to the cells within 10 min, which explains the cold lability of C theta on hemolysis. The structural basis of the cold lability was discussed through comparison of C theta with another nicked derivative of theta-toxin that was also obtained.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001427:Bacterial Toxins / Q000302:isolation & purification; D002942:Circular Dichroism; D003016:Clostridium perfringens; D003080:Cold Temperature; D004355:Drug Stability; D006460:Hemolysin Proteins; D011487:Protein Conformation; D014357:Trypsin
chemical_list: D000596:Amino Acids; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; C020452:Clostridium perfringens theta-toxin; D014357:Trypsin