The protein encoded by PPP1R14A (protein phosphatase 1 regulatory inhibitor subunit 14A) belongs to the protein phosphatase 1 (PP1) inhibitor family. This protein is an inhibitor of smooth muscle myosin phosphatase, and has higher inhibitory activity when phosphorylated. Inhibition of myosin phosphatase leads to increased myosin phosphorylation and enhanced smooth muscle contraction. Alternatively spliced transcript variants encoding different isoforms have been noted for PPP1R14A.