The PHACTR proteins share highest similarity in sequences surrounding the N- and C-terminal RPEL repeats and in the C-terminal actin- and PP1-binding domains. In situ hybridization of rat brain showed enrichment of Phactr1
in cerebral cortex, hippocampus, olfactory tubercle, nucleus accumbens, caudate-putamen, and piriform cortex.
Endogenous PP1 coprecipitated with ectopically expressed rat Phactr1 in human embryonic kidney cells. Phactr1 also coprecipitated with actin in rat brain lysates. Yeast 2-hybrid analysis of a series of Phactr1 C-terminal truncation mutants indicated that PP1 bound to Phactr1 near the C terminus, while actin bound in a region containing RPEL repeats 2 and 3.