Characterization of the lysosomal cystine transport system in mouse L-929 fibroblasts
We characterize here a lysosomal cystine transporter in mouse L-929 fibroblasts. Granular fractions from cells preloaded with cystine demonstrated countertransport that showed no dependence on Na+ or K+. The Michaelis constant for infinite-trans influx was 0.27 +/- 0.06 mM (n = 3), and a nonsaturabl...
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Published in | The Journal of biological chemistry Vol. 265; no. 17; pp. 9888 - 9895 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Bethesda, MD
American Society for Biochemistry and Molecular Biology
15.06.1990
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Subjects | |
Online Access | Get full text |
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Summary: | We characterize here a lysosomal cystine transporter in mouse L-929 fibroblasts. Granular fractions from cells preloaded with
cystine demonstrated countertransport that showed no dependence on Na+ or K+. The Michaelis constant for infinite-trans influx
was 0.27 +/- 0.06 mM (n = 3), and a nonsaturable component of cystine entry was observed with Kd = 0.8-1.8 nmol of cystine.min-1.unit
of hexosaminidase-1.mM-1. We found no evidence that cystine was also carried on any of the other known lysosomal amino acid
transporters. Over 50 analogs were tested for their ability to inhibit countertransport. The inhibition constants are reported
for selenocystine, cystathionine, selenomethionine, and leucine. Significant requirements for recognition by the transporter
were the presence of amino groups, L configuration, and a chain length not greater than eight atoms. A net positive or negative
charge was not required. Some di- as well as tetrapolar amino acids were recognized. We have surmised that the binding site
has polar and apolar domains, the latter being large enough to accommodate branching on C-3 and the substitution of selenium
or carbon in place of sulfur. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(19)38755-1 |