Fig. 4
The SH3 domain of ASPP binds to the PP1 C-tail. a Alignment of the C-termini of human and Drosophila PP1s. PP1α13C and PP1α87B have shorter C-termini that lack the PxxPxR motif (class II SH3 domain binding motif). All human PP1 isoforms possess this motif. The PxxPxR motif is highlighted in grey. Positively charged residues after the PPII are highlighted in blue. b, c Western blots of co-IP experiments from lysates of transfected S2 cells, probed with indicated antibodies. b PP1α96A and PP1β9C need their C-termini for efficient binding to ASPP. PP1α96A-ΔC lacks residues 304–327 and PP1α9C-βC lacks residues 304–330. c The SH3 domain of ASPP is required for binding to PP1α96A and PP1β9C. The W987K mutation in the ASPP SH3 domain (ASPPWK) reduces binding to PP1α96 A and PP1β9C but not PP1α13C and PP1α87B, which do not have the class II SH3 domain binding motif. d Western blots of co-IP experiments from lysates of transfected S2 cells, probed with indicated antibodies
