PPP1R12B (MYPT2) is a critical regulatory subunit of protein phosphatase 1, primarily functioning in muscle tissues to control myosin phosphatase activity and calcium sensitivity of contraction. Its tissue-specific expression, particularly enrichment in heart and skeletal muscle, along with multiple alternatively spliced isoforms, enables specialized roles in different cellular contexts. The protein's ankyrin repeats and C-terminal kinase-interacting domain facilitate its function as a molecular scaffold that directs PP1 catalytic activity toward specific substrates.