Cloning and characterization of Bδ, a novel regulatory subunit of protein phosphatase 2A

Variable regulatory subunits of protein phosphatase 2A (PP2A) modulate activity, substrate selectivity and subcellular targeting of the enzyme. We have cloned a novel member of the B type regulatory subunit family, Bδ, which is most highly related to Bα. Bδ shares with Bα epitopes previously used to generate subunit-specific antibodies. Like Bα, but unlike Bβ and Bγ which are highly brain-enriched, Bδ mRNA and protein expression in tissues is widespread. Bδ is a cytosolic subunit of PP2A with a subcellular localization different from Bα and may therefore target a pool of PP2A holoenzymes to specific substrates.