STRUCTURAL PERSPECTIVES OF PHOSPHOLAMBAN, A HELICAL TRANSMEMBRANE PENTAMER

Phospholamban is a 52-amino-acid protein that assembles into a pentame r in sarcoplasmic reticulum membranes. The protein has a role in the r egulation of the resident calcium ATPase through an inhibitory associa tion that can be reversed by phosphorylation. The phosphorylation of p hospholamban is initiated by beta-adrenergic stimulation, identifying phospholamban as an important component in the stimulation of cardiac activity by beta-agonists. It is this role of phospholamban that has m otivated studies in recent decades. There is evidence that phospholamb an may also function as a Ca2+-selective ion channel. The structural p roperties of phospholamban have been studied by mutagenesis, modeling, and spectroscopy, resulting in a new view of the organization of this key molecule in membranes.