Figure 2.

Myriad of PP2A/PPP2-holoenzymes generated from different combinations of catalytic and regulatory subunits. PP2A-holoenzymes are composed of a catalytic subunit (C) a scaffold protein (A/PR65) and any one of several targeting/regulatory proteins (B). There are two isoforms of the A and two isoforms of the C (α, β) subunits. The B-regulatory/targeting subunits are derived from one of four structurally unrelated families (B/B55; B’/B61; B”; B’”/93/110). Each of the different B families contains several isoforms, some of which are expressed in a tissue or developmentally specific manner. Given the existence of two isoforms of A, two isoforms of C and at least 18 different B subunits, >75 different trimeric forms of PPP2 can be generated with the known proteins. Table 1 provides a cross reference for the old and new (assigned based on the gene) names for the A, B and C subunits