Reduction of transducin GAP level in GAPux mouse retinas. As shown previously by Keresztes et al. (2004), inactivating one copy of the R9AP gene leads to a noticeable reduction of transducin GAP level. (A) Representative immunoblot simultaneously probed for RGS9-1, Gβ5-L, Gβ5-S, Gβ1, and GAPDH in 10 µg of retinal extracts derived from WT, R9AP heterozygous knockout (Het), and compound R9AP and RGS9-1 heterozygous (ux) mice. (B) Representative immunoblot simultaneously probed for RGS9-1, PDE6β, and GAPDH in WT and ux retinal extracts. (C) Quantification of RGS9-1 level for experiments described in A, showing in Het (middle bar) and ux (right bar) mouse retinas a decrease to 51 ± 3 and 34 ± 3 (mean ± SEM) percent of WT level (left bar). GAPDH level was used for normalization. Similar degree of reduction was seen in Gβ5-L level but not in Gβ5-S or Gβ1 level (not depicted). (D) Quantification of PDE6β expression relative to GAPDH level in experiments of B showed a comparable level in ux retinal extracts to that of WT at 95 ± 7%, while RGS9-1 level dropped to 37 ± 3% (n =3). Error bars are SEMs.