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The involvement of sodium in the function of the human amino acid transporter ASCT2
Author(s) -
Mazza Tiziano,
Scalise Mariafrancesca,
Pappacoda Gilda,
Pochini Lorena,
Indiveri Cesare
Publication year - 2021
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.14224
Subject(s) - transporter , chemistry , amino acid , cysteine , alanine , sodium , biophysics , stoichiometry , recombinant dna , biochemistry , serine , biology , phosphorylation , enzyme , organic chemistry , gene
Alanine, serine, cysteine transporter 2 (ASCT2) is a membrane amino acid transporter with relevance to human physiology and pathology, such as cancer. Notwithstanding, the study on the ASCT2 transport cycle still has unknown aspects, such as the role of Na + in this process. We investigate this issue using recombinant hASCT2 reconstituted in proteoliposomes. Changes in the composition of purification buffers show the crucial role of Na + in ASCT2 functionality. The transport activity is abolished when Na + is absent or substituted by Li + or K + in purification buffers. By employing a Na + fluorometric probe, we measured an inwardly directed flux of Na + and, by combining fluorometric and radiometric assays, determined a 2Na + : 1Gln stoichiometry. Kinetics of Na + transport suggest that pH‐sensitive residues are involved in Na + binding/transport. Our results clarify the role of Na + on human ASCT2 transporter activity.