Fig. 1. Gi, Gq and Gs proteins localize to the cortex of sea urchin eggs. (A-D) Mature sea urchin eggs labeled with hyalin (cortical granule marker; red) and anti-G antibodies (green). A single cell is outlined in B. (a-d) Fragments of images in A-D (outlined by dotted lines) showing red and green channels separately. Immunolocalizations in thick paraffin sections were performed as described in the Materials and Methods. Bar, 50 µm. (E) Cell-surface complex (csc; plasma membrane and cortical granules) and whole eggs lysate (e) protein samples were analyzed by immunoblotting (loading µg amounts indicated below lanes). Positions of molecular weight markers (in kDa) are shown at the left. The blots were probed with anti-MGB (1:1000) (Haley and Wessel, 2004), anti-YP30 (1:4000) (Wessel et al., 2000), anti-Gi (1:500), anti-Gq (4.5 µg/ml), anti-Gs (1:500) and anti-G12 (1:100) (Voronina and Wessel, 2004).