This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Plagemann, P G Articles by Woffendin, C Search for Related Content PubMed PubMed Citation Articles by Plagemann, P G Articles by Woffendin, C

 Previous Article  |  Next Article 

Mol Cell Biol. 1987 January; 7(1): 160-166

Residual nitrobenzylthioinosine-resistant nucleoside transport in a transport mutant (AE1) of S49 murine T-lymphoma cells.

ABSTRACT

The uptake of various nucleosides by S49 mouse T-lymphoma cells and that by a single-step nucleoside transport-defective mutant thereof (AE1) were compared. Residual nucleoside entry into AE1 cells occurred via two routes, nonmediated permeation and saturable, non-concentrative transport with broad substrate specificity and a Michaelis-Menten constant approximating that for thymidine transport in wild-type cells. However, in contrast to nucleoside transport in wild-type cells, residual nucleoside transport in AE1 cells was resistant to inhibition by nitrobenzylthioinosine. In its properties the latter resembled nitrobenzylthioinosine-resistant nucleoside transport observed in other types of mammalian cells. It amounted to less than 1% of the total nucleoside transport activity of wild-type S49 cells. The results indicate that nitrobenzylthioinosine-resistant and -sensitive nucleoside transports are genetically distinguishable. In wild-type cells, the salvage of thymidine, when present at concentrations higher than 1 to 10 microM, was limited by phosphorylation, because of the saturation of thymidine kinase. In AE1 cells, entry into the cells mainly limited thymidine salvage, but at high thymidine concentrations the combined entry via residual transport and nonmediated permeation was sufficiently rapid to support intracellular thymidine phosphorylation at rates comparable to those observed in wild-type cells.