Regions of Salmonella typhimurium flagellin essential for its polymerization and excretion.

Immunological methods were used to examine the flagellin production of Salmonella typhimurium strains that carried a mutation in one of the two possible genes for flagellin (H1 or H2) and also were incapable of expressing the other gene. Some mutants produced flagellin that was excreted into the culture medium; others accumulated flagellin intracellularly. These two phenotypes were detected in both H1 and H2 mutants. The mutation sites were mapped on the corresponding deletion map (consisting of 21 segments in the case of H1 and 31 segments in the case of H2). H1 and H2 mutations causing excretion of flagellin were clustered mainly in segment 12 and segment 6 from the proximal end, respectively, suggesting that the corresponding segments of the flagellins play a role in polymerization. Mutations causing accumulation in the cytoplasm were clustered in segments 19 to 21 of the H1 map and in segments 25 to 29 of the H2 map, suggesting that an essential region for flagellin transport exists toward the C terminus of flagellin.