The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 

Chirality differences in amino acid retention and release from acid-extractable pool of cultured mammalian cells.

In previous work, no chiral differences were found between D and L enantiomers of Leu in their ability to displace one another from the acid-extractable pool in mammalian cells. Recent evidence suggested otherwise. Our aim is to examine whether, in physiological range, D-amino acids have an equivalent ability to displace L-amino acids from the acid-extractable pool of HeLa cells, and vice versa. In the Millimolar range, D-Leu and L-Leu have similar uptake and displacement properties with regard to the acid-extractable pool in HeLa cells, despite only the latter isomer being incorporated into protein. Below millimolar concentration however, a distinct difference was found in the displacement of tritium-labelled L-Leu from the pool by unlabelled D-Leu compared with unlabelled L-Leu. Thus, unlabelled L-Leu in the external medium at 10(-4) or 10(-5) M displaced and equivalent amount of label from the pool ad D-Leu introduced at a concentration approx. one order of magnitude higher, respectively. Reciprocal experiments, in which the acid-extractable pool was preloaded with 3H-D-Leu, confirmed this finding. The chirality difference was noted whether pool prelabelling was carried out at 37 or 0 degrees C; but in order to avoid the complications of active transport mechanisms, the competition work reported here was done at 0 degrees C. Similar chirality differences were observed with other hydrophobic amino acids, including His, Ile, and Phe, such as, preferential displacement by the L-Leu racemer compared with the D-Leu racemer below mM levels. This was also true for the D and L forms of the non-utilisable isomer of Leu, norleucine (nLeu). We conclude that D-forms of hydrophobic amino acids have lower affinity for similar or the same intracellular binding sites involved in the acid-extractable pool than in their L-forms. The significance of these findings to amino acid pools in cells, and to the predominance of L-forms of amino acids in the biosphere is considered[1]

References

  1. Chirality differences in amino acid retention and release from acid-extractable pool of cultured mammalian cells. Wheatley, D.N., Slater, J., Love, E.M., Miseta, A. Int. J. Biochem. Cell Biol. (1996) [Pubmed]
 
WikiGenes - Universities