Regulates myosin phosphatase activity. Augments Ca(2+) sensitivity of the contractile apparatus. {ECO:0000269|PubMed:11067852, ECO:0000269|PubMed:9570949}. This is the function of Ensembl gene identifier ENSG00000077157 (PPP1R12B, protein phosphatase 1 regulatory subunit 12B).