Nature 493, 97–100 (2013); doi:10.1038/nature11655

In this Letter, there were two typographical errors in both the Methods Summary and the full Methods. The concentration of urethane should be 1.5 g per kg of body weight, not 1.5 mg. In addition, the intracellular solutions contained 0.3 mM Na3GTP, not Na2ATP. These errors have been corrected in the HTML and PDF versions of the manuscript. There were also errors in Supplementary Fig. 8, in which we inadvertently combined data from the wrong trial types to assess current–voltage (IV) linearity. This has been corrected in the Supplementary Information of the original manuscript, and does not affect the results or conclusions.