CaM-KII increased the contribution of high-conductance states in single-channel activity. Single-channel recordings (*Top*), distribution of channel conductances (*Middle*), and channel openings (*Bottom*) were obtained from cells expressing GluR1 alone (*A*), from cells expressing GluR1 coexpressed with CaM-KII (*B*), or from the Ser-831-to-Asp mutant (*C*). For single-channel recordings, eight traces every 100 ms were superimposed, recorded at membrane potentials of −101 mV (A), −128 mV (*B*), and −125 mV (*C*). For comparison, currents in *A–C* were scaled by conductance and show the same four conductance states in all situations. Note the different scales for the same calibration of 1 pA in *A–C*. Each conductance histogram was fitted by the sum of four Gaussian functions (smooth curves), which are shown individually by dotted lines. Their mean values were, for *A*, 9.3 pS (contribution of 26.8%), 13.5 pS (56.8%), 22.2 pS (12.4%), and 27.3 pS (4%); for *B*, 8.6 pS (23.7%), 14.1 pS (30.3%), 23.1 pS (24%), and 27.1 (22%); and, for *C*, 9.6 pS (0.8%), 13.1 pS (13.7%), 21.3 pS (57.5%), and 26.1 pS (28%). Calculated weighted single-channel conductances were 13.8 pS (*A*), 17.9 pS (*B*), and 21.4 pS (*C*). Each distribution of open times was fitted by the sum of two exponentials with time constants of 0.24 ms (contribution of 73%) and 2.4 ms (*A*), 0.36 ms (71%) and 2.4 ms (*B*), and 0.29 ms (52%) and 2.5 ms (*C*).

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