Purification, characterization, and partial covalent structure of Escherichia coli adhesive antigen K99

The adhesive antigen K99 of enterotoxigenic Escherichia coli strains of calf origin was isolated and purified. The K99 fimbriae were removed from the cells by heat treatment, concentrated by precipitation with ammonium sulfate, and purified by gel filtration on Sepharose CL-4B and treatment with deoxycholate. The purified K99 antigen was composed of protein subunits with a molecular weight of 18,500 and had an isoelectric point of 9.5. The N-terminal amino acid sequence, as well as the composition of the C-terminal part of the K99 protein subunits, was determined.