Protein Phosphatase 1, Regulatory Subunit 16A (PPP1R16A)

Mypt3 contains a PP1-binding site, followed by 5 ankyrin repeats, a putative Walker A ATP/GTP-binding site, 2 SH3-binding sites, and a C-terminal CAAX box farnesylation motif. Northern blot analysis detected a transcript of about 3.2 kb in mouse heart, brain, lung, liver, skeletal muscle, and testis. Mypt3 was weakly expressed in kidney, but absent from spleen. A transcript of about 2.8 kb was detected in mouse preadipocyte fibroblasts and differentiated adipocytes, with slight upregulation during differentiation. Western blot analysis detected Mypt3 protein expressed in the same mouse tissues and cells. Endogenous PP1 from mouse fibroblast cell line lysates specifically interacted with Mypt3. Recombinant Mypt3 inhibited purified PP1 activity toward phosphorylase a, myosin light chain, and myosin substrates in vitro.