OBJECTIVE The di-leucine motif exists in the intracellular domains of certain cell surface receptors, participating in the receptor-mediated endocytosis. The present study was aimed at determining the role of the di-leucine motif in class A scavenger receptor (SR-A)-mediated ligand endocytosis. METHODS AND RESULTS cDNA coding for a mutant (SR-A mutant N3132LM) with deletion of the di-leucine ...

Kinetics of leucine and its oxidation were determined in human pregnancy and in the newborn infant, using stable isotopic tracers, to quantify the dynamic aspects of protein metabolism. These data show that in human pregnancy there is a decrease in whole-body rate of leucine turnover compared with nonpregnant women. In addition, data in newborn infants show that leucine turnover expressed as pe...

Linear growth in children is sensitive to nutritional status. Amino acids, in particular leucine, have been shown to regulate cell growth, proliferation, and differentiation through the mammalian target of rapamycin (mTOR), a nutrient-sensing protein kinase. Having recently demonstrated a role for mTOR in chondrogenesis, we hypothesized that leucine restriction, acting through mTOR, would inhib...

Leucine is a well-known activator of the mammalian target of rapamycin (mTOR). Because mTOR signaling regulates several aspects of metabolism, the potential of leucine as a dietary supplement for treating obesity and diabetes mellitus has been investigated. The objective of the present review was to summarize and discuss the available evidence regarding the mechanisms and the effects of leucine...

In previous studies we have reported that a) marked sensitivity to leucine hypoglycemia can be induced consistently in healthy subjects after the oral administration of sulfonylureas, compounds that are known to stimulate islet cell activity (1), b) a modest but significant hypoglycemic effect can be produced by administering leucine to healthy subjects without sulfonylurea pretreatment (1, 2),...

Based on a mass-balance model, a surrogate measure of the whole body leucine transport into and out of cells under steady-state conditions was calculated as u/ΔTTR, where u is the infusion rate of (stable label) leucine tracer and ΔTTR is the difference between the tracer-to-tracee ratio of extracellular and intracellular leucine. The approach was evaluated in ten healthy subjects [8 males and ...

1. The fractional rate of protein synthesis (FSR) in tissues of nine growing lambs (4-5 months of age) was estimated following continuous infusion of L-[4,5-3H]leucine for a period of 7 h. Minimum and upper estimates of FSR were obtained assuming that the specific radioactivity (SRA) of leucine in blood plasma and tissue homogenate respectively defined that of leucyl tRNA. 2. Mean upper estimat...

Leucyl transfer ribonucleic acid synthetase (EC 6.1.1.4, L-leucine: tRNA ligase (AMP)) has been purified from Escherichia coli and is free of other aminoacyl-tRNA synthetases, tRNA-methylating enzymes, and CpCpA-adding enzymes. Several criteria suggest that there is one synthetase with specikity for two forms of leucine-specik tRNA which can be separated by countercurrent distribution: purifica...

The postprandial rise in amino acids, particularly leucine, stimulates muscle protein synthesis in neonates. Previously, we showed that a 1-h infusion of leucine increased protein synthesis, but this response was not sustained for 2 h unless the leucine-induced decrease in amino acids was prevented. To determine whether a parenteral leucine infusion can stimulate protein synthesis for a more pr...

We describe a new family of discrete supramolecules comprising leucine-zipper peptides noncovalently assembled upon cognate leucine zippers fused to a dendrimer core. Circular dichroism and sedimentation equilibrium experiments clearly demonstrate that each leucine-zipper dendrimer (D-EZ4 or D-KZ4) can noncovalently display four leucine zippers on their surface that can be utilized for the mult...