Transporter activity of cysteine mutant with only intact disulfide bridge (Cys-249 and Cys-321 residues) decreases in the presence of DTT, TCEP and GSH.

<p>Wild type and mutant SNAT4 expressing oocytes were incubated with DTT (0–10 mM) (A), TCEP (0–10 mM) (B) and 10 mM GSH (D). [³H]-alanine uptake assay was performed. Under reducing conditions, L-alanine transport in mutant SNAT4 significantly decreased. (C) Mutant SNAT4 expressing oocytes were incubated with 1 mM TCEP in the presence and absence of 0.02% H₂O₂. Under oxidative conditions, L-alanine transport in mutant SNAT4 was significantly recovered. Data is presented as mean ± SEM, n = 3 (∼ 10 oocytes/sample). Treated versus untreated control of the mutant, ***, P<0.001.