Evidence for the presence of phospholamban in the endoplasmic reticulum of smooth muscle

Luc Raeymaekers, Larry R. Jones

Research output: Contribution to journalArticle

50 Scopus citations


In microsomal vesicles isolated from several smooth muscles many polypeptides were phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase. In pig stomach and in rabbit and dog aorta components of Mr 22 000 and 11 000 were identified as forms of phospholamban. These polypeptides were, however, not observed in pig aorta. These phospholamban-like polypeptides presented the same electrophoretic mobility in sodium dodecyl sulphate gels as cardiac phospholamban, and the 22 000 Mr form showed a similar reaction to heat treatment in sodium dodecyl sulphate. Antibodies against purified canine cardiac phospholamban cross-reacted with the 22 000 and 11 000 Mr phosphorylatable polypeptides from smooth muscle membranes. Subcellular fractionation of porcine stomach smooth muslce indicated that phospholamban was present in the membranes of the endoplasmic reticulum and not in the plasma membranes. Phospholamban was also phosphorylated by an endogenous calcium-calmodulin-dependent protein kinase and by an endogenous cyclic AMP-dependent kinase. It is concluded that the endoplasmic reticulum of many, but possibly not all, smooth muscles contains phospholamban. However, the physiological role of phospholamban in smooth muscle remains to be established.

Original languageEnglish (US)
Pages (from-to)258-265
Number of pages8
JournalBBA - General Subjects
Issue number2
StatePublished - Jun 19 1986


  • (Smooth muscle)
  • Phospholamban
  • Protein phosphorylation

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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