Barak Z, Gilbarg C
J Bacteriol. 1975 Jun;122(3):1200-7. doi: 10.1128/jb.122.3.1200-1207.1975.
Trileucine is utilized as a source of leucine for growth of strains of Escherichia coli K-12 that are deficient in the oligopeptide transport system (Opp). Trithreonine is toxic to E. coli K-12. Opp- mutants of E. coli K-12 retain complete sensitivity to this tripeptide. Moreover, E. coli W, which is resistant to trithreonine, can utlize this tripeptide as a threonine source and this capability is fully maintained in E. coli W (Opp-). A spontaneous trithreonine-resistant mutant of E. coli K-12 (Opp-) has been isolated that has an impaired growth response to trileucine and is resistant to trithreonine. Trileucine competes with the uptake of trithreonine as measured by its ability to relieve trithreonine toxicity in E. coli K-12. It is concluded that trileucine as well as trithreonine are transported into E. coli K-12 or W by a common uptake system that is distinct from the Opp system. Trimethionine can act as a competitor of trileucine or trithreonine-supported growth and as an antagonist of trithreonine toxicity in Opp- mutants. It is concluded that trimethionine is recognized by the trileucine-trithreonine transport system. Trithreonine, trimethionine, and trileucine are also transported by the Opp system, as they all relieve triornithine toxicity towards E. coli W and compete with tetralysine utilization as lysine source for growth of a lysine auxotroph of this strain.
三亮氨酸被用作缺乏寡肽转运系统（Opp）的大肠杆菌K-12菌株生长所需亮氨酸的来源。三苏氨酸对大肠杆菌K-12有毒。大肠杆菌K-12的Opp-突变体对这种三肽仍保持完全敏感性。此外，对三苏氨酸有抗性的大肠杆菌W可以利用这种三肽作为苏氨酸来源，并且这种能力在大肠杆菌W（Opp-）中完全保留。已分离出一株大肠杆菌K-12（Opp-）的自发三苏氨酸抗性突变体，它对三亮氨酸的生长反应受损且对三苏氨酸有抗性。通过三亮氨酸缓解大肠杆菌K-12中三苏氨酸毒性的能力来衡量，三亮氨酸与三苏氨酸的摄取相互竞争。得出的结论是，三亮氨酸和三苏氨酸通过一种不同于Opp系统的共同摄取系统转运到大肠杆菌K-12或W中。三甲硫氨酸可以作为三亮氨酸或三苏氨酸支持生长的竞争者，并且作为Opp-突变体中三苏氨酸毒性的拮抗剂。得出的结论是，三甲硫氨酸被三亮氨酸-三苏氨酸转运系统识别。三苏氨酸、三甲硫氨酸和三亮氨酸也通过Opp系统转运，因为它们都能缓解三鸟氨酸对大肠杆菌W的毒性，并与四赖氨酸作为该菌株赖氨酸营养缺陷型生长的赖氨酸来源的利用相互竞争。
