A regulatory mutant, KA600 (
ilvC8 livR3::Tn
10), derepressed in the transport of branched-chain amino acids, was isolated from a strain KA931 (
ilvC8) of
Salmonella typhimurium LT2, after mutagenesis with tetracycline resistance transposon, Tn
10. KA600 still carried P22-phage genome used as a vector in mutagenesis, and when grown on an agar medium, it segregated frequently phage-free clones possessing either a tetracycline-resistance (
tetR) or a tetracycline-sensitive (
tets) trait. Two of these segregant clones, KA601 (
ilvC8 livR3::Tn
10) and KA602 (
ilvC8 livR3), were not different from KA600 in the mode of L-isoleucine transport. Levels of L-isoleucine and L-leucine uptake by KA610 (
livR3::Tn
1O), an Ilv
+ transductant of KA601, were increased 1.4- to 2.0-fold over those of the wild-type. These uptake abilities were not repressed at all by 5mM glycyl-L-leucine. Activity of the branched- chain amino acid binding protein(s) of KA602 released by osmotic-shock was several times higher than that of KA931, although the activity of the former was repressible by glycyl-L-leucine to some extent. The
livR locus was mapped in the region of 75 to 77 units on the genetic map of
S. typhimurium. Nature of
livR mutation distinct from a similar regulatory mutation,
liv-231 is discussed.
抄録全体を表示