Correction

The following clarification is necessary for this article:

 The last line of discussion:

 This Arg¹⁴⁸ also participates in the formation of a salt bridge.

should be deleted and replaced with:

Note Added in Proof

Recently it was shown that this Arg¹⁴⁸ also participates in the formation of a salt bridge. (Yang, J., M. Yu, Y.N. Jan, and L.Y. Jan. 1997. Stabilization of ion selectivity filter by pore loop ion pairs in an inwardly rectifying potassium channel. Proc. Natl. Acad. Sci. USA. 94:1568–1572.)