Figure 2.
Neutralization of Arg-41 and Arg-311 shifts titration of Lys-80 to the alkaline pH range by several pH units. (A) Cartoon summarizing the shift in pH0.5 (ΔpH0.5) observed on neutralization of the Arg/Lys residues in the N and C termini conserved among all Kir proteins. Note that only R41Q and R311Q led to shifts in pH0.5 (ΔpH0.5) >3 pH units. (B) Patch recordings from oocytes expressing Kir1.1(R41Q) (Upper) and Kir1.1(R311Q) (Lower) at the pHis indicated. Protocol as in Fig. 1. (C) Immunostaining of FLAG-tagged Kir1.1(R311Q) and Kir1.1 wild-type channels. Note staining of the plasma membrane in oocytes expressing either the Kir1.1 wild-type or mutant subunit, whereas no staining was obtained in a control oocyte (water injected). (D) Rescue of channel activity by replacement of Lys-80 with methionine in R41Q, R311Q, and R41,311Q channels. Recordings as in A from Kir1.1(R41Q,K80M), Kir1.1(R311Q,K80M), and Kir1.1(R41, 311Q,K80M) at the pHis indicated.