Fig. 2
From: The emerging roles of phosphatases in Hedgehog pathway
Subunit composition of PP2A holoenzyme. a PP2A holoenzyme is a heterotrimeric complex, consisting of three subunits: a scaffolding subunit A, a regulatory subunit B, and a catalytic subunit C, in which B subunit confers the specificity of substrates, by providing distinguished docking surfaces (represented by B1 and B2) towards the active sites (indicated by red asterisks) of C subunit, to allow the binding of specific substrate proteins (S1 and S2, respectively). b Drosophila genome encodes a single A subunit and a single C subunit, but four B subunits. In mammals, there are two A subunits, two C subunits, and more than 20 B subunits. The B subunits are classified into at least three families: B55, B56, and PR72, of which B56 family includes the largest number of members, and is further divided into two subgroups: Wdb/α,β,ε and Wrd/γ,δ. The diversity of B subunit contributes to the selection of various PP2A substrates. Tws, Twins; Wdb, Widerborst; Wrd, Well-rounded