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Among flagellar mutants of Escherichia coli, flaM or flaU mutants form basal bodies lacking the outer P and L rings, whereas flaY mutants predominantly form basal bodies lacking the L ring. In these mutants, hooks and filaments are occasionally assembled onto these incomplete basal bodies. When the hook protein gene, flaFV, of Salmonella typhimurium was cloned on the multicopy plasmid pBR322 and introduced into these mutants, the efficiency with which cells assembled hooks and filaments onto the incomplete basal bodies increased significantly. Such cells formed characteristic dotted swarms on semisolid plates, indicating that cells carrying flagella without the outer rings are weakly motile because of poor function of their flagella, a low flagellar number per cell, or both of these defects. FlaV mutants also produced incomplete basal bodies lacking the outer rings, but assembly of hooks and filaments did not occur in these mutants even after introduction of the plasmid carrying flaFV of S. typhimurium. The failure in the case of flaV mutants was attributed to their inability to modify the rod tip to the structure competent for assembly of hook protein.

The flagellar genes flaFV, flaFVII, and flaFVIII of Salmonella typhimurium were cloned, and their presence on a given plasmid was verified by complementation of Escherichia coli mutants defective in the homologous genes. The gene products were identified by radiolabeling in a minicell system as being proteins of the following molecular masses: FlaFV, 42 kilodaltons (kDa); FlaFVI, 32 kDa; FlaFVII, 30 kDA; and FlaFVIII, 27 kDa. These data, together with isoelectric focusing data, confirm gene product assignments of flagellar components made indirectly from mutant studies. Flagellar components are transported by either a signal peptide-dependent or a flagellar-specific pathway. Consistent with its location in the outer membrane ring of the basal body, protein FlaFVIII seems to use the signal peptide-dependent pathway, since it was synthesized in a precursor form and processed, presumably by peptide cleavage, to a mature form; the maturation process was inhibited by addition of a proton ionophore. Proteins synthesized in minicells were localized as follows: FlaFVI was localized to the soluble fraction (cytoplasm); pre-FlaFVIII and FlaFVIII were localized to the particulate fraction (membrane or high-molecular-weight aggregate); FlaFV and FlaFVII were localized to both fractions. The significance of these locations in terms of known or suspected roles in the flagellar apparatus is discussed.

Kinetics of the transport systems common for entry of L-isoleucine, L-leucine, and L-valine in Salmonella typhimurium LT2 have been analyzed as a function of substrateconcentration in the range of 0.5 to 45 muM. The systems of transport mutants, KA203 (ilvT3) and KA204 (ilvT4), are composed of two components; apparent Km values for uptake of isoleucine, leucine, and valine by the low Km component are 2 muM, 2 to 3 muM, and 1 muM, respectively, and by the high Km component 30 muM, 20 to 40 muM, and 0.1 mM, respectively. The transport system(s) of the wild type has not been separated into components but rather displays single Km values of 9 muM for isoleucine, 10 muM for leucine, and 30 muM for valine. The transport activity of the wild type was repressed by L-leucine, alpha ketoisocaproate, glycyl-L-isoleucine, glycyl-L-leucine, and glycyl-L-methionine. That for the transport mutants was repressed by L-alanine, L-isoleucine, L-methionine, L-valine, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, glycyl-L-alanine, glycyl-L-threonine, and glycyl-L-valine, in addition to the compounds described above. Repression of the mutant transport systems resulted in disappearance of the low Km component for valine uptake, together with a decrease in Vmax of the high Km component; the kinetic analysis with isoleucine and leucine as substrates was not possible because of poor uptake. The maximum reduction of the transport activity for isoleucine was obtained after growing cells for two to three generations in a medium supplemented with repressor, and for the depression, protein synthesis was essential after removal of the repressor. The transport activity for labeled isoleucine in the transport mutant and wild-type strains was inhibited by unlabeled L-alanine, L-cysteine, L-isoleucine, L-leucine, L-methionine, L-threonine, and L-valine. D-Amino acids neither repressed nor inhibited the transport activity of cells for entry of isoleucine.