Protein Phosphatase 1, Regulatory Subunit 12B (PPP1R12B)

The holoenzyme of smooth muscle myosin phosphatase consists of 3 subunits: the catalytic subunit PP1c-delta (PPP1CB), and 2 putative regulatory subunits, MYPT (myosin phosphatase target) and M20. MYPT2 contains 7 ankyrin repeats near the N terminus and C-terminal leucine zipper motifs. Northern blot analysis revealed that MYPT2 is expressed as multiple transcripts in a tissue-specific pattern, with the strongest expression in heart and skeletal muscle. Western blots detected the 125-kD MYPT2 protein only in brain and heart, in contrast to MYPT1, which is widely distributed in human tissues. In vitro, recombinant proteins containing the N-terminal two-thirds of either MYPT2 or MYPT1 bound to PP1c-delta and increased activity toward phosphorylated myosin light chain.