Homoserine is transported by a single system which it shares with alanine, cysteine, isoleucine, leucine, phenylalanine, threonine, tyrosine, and valine. The evidence for this being the sole system for homoserine transport is (i) a linear double reciprocal plot showing a homoserine Km of 9.6 x 10-6 M, (ii) simultaneous reduction by 85% of homoserine and branched chain amino acid uptake in a mutant selected for its inability to transport homoserine, and (iii) simultaneous reduction by 94% of the uptake of homoserine and the branched chain amino acids by cells grown in millimolar leucine. Threonine, in addition to sharing the above system with homoserine, is transported by a second system shared with serine. The evidence for this second system consists of (i) incomplete inhibition of threonine uptake by any single amino acid, (ii) only 70% loss of threonine uptake in the mutant unable to transport homoserine, and (iii) only 40% reduction of threonine uptake when cells are grown in millimolar leucine. In this last case, the remaining threonine uptake can only be inhibited by serine and the inhibition is complete.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Bacteriology|
|State||Published - 1974|
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology