Biophysical interaction between phospholamban and protein phosphatase 1 regulatory subunit GM

Regulation of the sarco(endo)plasmic reticulum Ca2+- ATPase (SERCA 2a) depends on the phosphorylation state of phospholamban (PLB), When PLB is phosphorylated, its inhibitory effect towards SERCA 2a is relieved, leading to an enhanced myocardial performance, This process is reversed by a sarcoplasmic reticulum (SR)-associated type 1 protein phosphatase (PP1) composed of a catalytic subunit PP1C and a regulatory subunit Gill, Human Gill and PLB have been produced in an in vitro transcription/translation system and used for co-immunoprecipitation and biosensor experiments, The detected interaction between the two partners suggests that cardiac PP1 is targeted to PLB via GM and we believe that this process occurs,vith the identified transmembrane domains of the tno proteins, Thus, the interaction between PLB and GM may represent a specific way to modulate the SR function in human cardiac muscle. (C) 1998 Federation of European Biochemical Societies.