New mutations and phenotypes associated with glutamate and aspartate transport in Chinese hamster ovary (CHO-K1) cells
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Two new Chinese hamster ovary cell (CHO-K1) mutants lacking amino acid transport System XAG− activity were isolated by [3H]aspartate suicide selection. These null mutants, Dd-B6 and Dd-B7, were analyzed by somatic cell hybridization, along with previously described partial-function mutants, Ed-A1 and Ed-B8. With respect to System XAG− activity, all four mutations fell into a single complementation group. By quantitative assay, the mutations in Ed-A1 and Ed-B8 behaved as simple recessives in fusions with wild type cells, while those in Dd-B6 and Dd-B7 were codominant. We have discovered that Ed-A1 and Ed-B8 are highly permeable to smal neutral molecules. This high permeability phenotype was dominant to wild-type. Northern, Southern, and Western analyses indicated that System XAG− in CHO is not closely related to any of the three well characterized glutamate transporters represented by GLT-1, EAAC1 or GLAST.
KeywordsGlutamate Wild Type Cell Chinese Hamster Ovary Cell Chinese Hamster Ovary Null Mutant
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