Transport of biosynthetic intermediates: homoserine and threonine uptake in Escherichia coli

B. A. Templeton, M. A. Savageau

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


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 languageEnglish (US)
Pages (from-to)1002-1009
Number of pages8
JournalJournal of Bacteriology
Issue number3
StatePublished - 1974
Externally publishedYes

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Immunology


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