Phospholamban (IPR005984)

Short name: PLB

Overlapping homologous superfamilies


Family relationships



Phospholamban (PLB) is a small protein (52 amino acids) that regulates the affinity of the cardiac sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) for calcium. PLB is present in cardiac myocytes, in slow-twitch and smooth muscle and is expressed also in aorta endothelial cells in which it could play a role in tissue relaxation. The phosphorylation/dephosphorylation of phospholamban removes and restores, respectively, its inhibitory activity on SERCA2a. It has in fact been shown that phospholamban, in its non-phosphorylated form, binds to SERCA2a and inhibits this pump by lowering its affinity for Ca2+, whereas the phosphorylated form does not exert the inhibition. PLB is phosphorylated at two sites, namely at Ser-16 for a cAMP-dependent phosphokinase and at Thr-17 for a Ca2+/calmodulin-dependent phosphokinase, phosphorylation at Ser-16 being a prerequisite for the phosphorylation at Thr-17.

The structure of a 36-amino-acid-long N-terminal fragment of human phospholamban phosphorylated at Ser-16 and Thr-17 and Cys36Ser mutated was determined from nuclear magnetic resonance data. The peptide assumes a conformation characterised by two alpha-helices connected by an irregular strand, which comprises the amino acids from Arg-13 to Pro-21. The proline is in a trans conformation. The two phosphate groups on Ser-16 and Thr-17 are shown to interact preferably with the side chains of Arg-14 and Arg-13, respectively [PMID: 12080135].

GO terms

Biological Process

GO:0006816 calcium ion transport

Molecular Function

GO:0042030 ATPase inhibitor activity
GO:0005246 calcium channel regulator activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.