Comparing expression and function of D935N(C113Y) and parent C113Y pumps. (A and B) Representative recordings of pump–channel currents induced by 100 nM palytoxin (PTX), at −50 mV with symmetrical 125-mM [Na⁺] solutions, in outside-out patches excised from oocytes injected with the same amounts of cRNA (30 ng α subunit plus 10 ng β subunit): (A) after 1 d of expression (black, C113Y: steady current amplitude, −1.2 ± 0.2 nA and n = 4; green, D935N: −1.1 ± 0.2 nA and n = 4), and (B) after 2 d (black, C113Y: −2.1 ± 0.2 nA and n = 15; green, D935N: −2.1 ± 0.1 nA and n = 8). (C) Ouabain-sensitive outward Na⁺/K⁺ transport currents at 15 mM K⁺_o in 125 mM Na⁺_o from the very same two C113Y-expressing (black stars) and D35N-expressing (green stars) oocytes from which the patch recordings in B were obtained. (D) Average outward pump currents in 15 mM K⁺_o and 125 mM Na⁺_o for C113Y (black stars; n = 12) and D935N (green stars; n = 9) after 2 d of expression, recorded in oocytes (including those of B and C) from the same batches that yielded the average excised-patch data in B.