The metabolism of an essential amino acid, isoleucine, by human leukemic and gradient-separated normal human leukocytes of various types and maturity was studied. Blood leukocytes were isolated and incubated with [U-’4CJ isoleucine. Separation of metabolic intermediates was accomplished by sequential extraction. The rate of isoleucine incorporation into protein by immature cells from untreated ...

Bacteria possess amino acid export systems, and Corynebacterium glutamicum excretes L-isoleucine in a process dependent on the proton motive force. In order to identify the system responsible for L-isoleucine export, we have used transposon mutagenesis to isolate mutants of C. glutamicum sensitive to the peptide isoleucyl-isoleucine. In one such mutant, strong peptide sensitivity resulted from ...

The leucine analogue 5',5',5',-trifluoroleucine (fluoroleucine) replaced leucine for repression of the isoleucine-valine biosynthetic enzymes in Salmonella typhimurium. In contrast, the analogue had no effect on derepression of the leucine biosynthetic enzymes in leucine auxotrophs grown on limiting amounts of leucine. The effect of fluoroleucine on repression appeared to be specific for leucin...

Because the abundance of functional molecules in RNA sequence space has many unexplored aspects, we compared the outcome of 11 independent selections, performed using the same affinity selection protocol and contiguous randomized regions of 16, 22, 26, 50, 70, and 90 nucleotides. All affinity selections targeted the simplest isoleucine aptamer, an asymmetric internal loop. This loop should be a...

Intraerythrocytic malaria parasites can obtain nearly their entire amino acid requirement by degrading host cell hemoglobin. The sole exception is isoleucine, which is not present in adult human hemoglobin and must be obtained exogenously. We evaluated two compounds for their potential to interfere with isoleucine utilization. Mupirocin, a clinically used antibacterial, kills Plasmodium falcipa...