Characterization of type 1 pili of Salmonella typhimurium LT2

Abstract

Type 1 pili from S. typhimurium LT2 were purified and characterized. The pilus filaments were 6 nm in diameter and over 1 μm long. Estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of the pilin was 21,000. The isoelectric point of the filament was 4.1. Hydrophobic amino acids comprised 40.3% of the total amino acids of the pilin, which contained more porline, serine, and lysine than reported for the type 1 pilin of Escherichia coli. Purified pili agglutinated both horse and chicken erythrocytes and yeast cells but not bovine, sheep, or human erythrocytes. Horse erythrocyte agglutination was inhibited at lower concentrations by α-methyl-D-mannoside than by yeast mannane and D-fructose. Agglutination was not affected by D-galactose or sucrose. Results of the present study confirm the role of type 1 pili as Salmonella hemagglutinins and show chemical differences between the type 1 pili of S. typhimurium and E. coli.