CHARACTERIZATION OF A HIGHLY TOXIC, LARGE MOLECULAR-SIZE HEAT-STABLE ENTEROTOXIN PRODUCED BY A CLINICAL ISOLATE OF YERSINIA-ENTEROCOLITICA

A novel heat-stable enterotoxin (ST) designated as Y-STc was purified to homogeneity from the culture supernatant of a pathogenic strain of Yersinia enterocolitica serotype O3 and its amino acid sequence was determined. The mature Y-STc was found to consist of 53 amino acid residues, which includes the putative pro-sequence. The molecular weight of Y-STc was 5638 and constituted the largest molecular size in the family of currently known STs. The minimum effective dose of purified Y-STc in the suckling mouse assay was 0.6 ng (0.1 pmol), indicating that, despite the long sequence, Y-STc is the most toxic in the ST family.