Structure and Function of Phospholamban

Phospholamban is a homopentamer, each subunit consisting of 52 amino acids. The subunits consist of a 30-residue N-terminal hydrophilic region containing the phosphorylation sites, and a C-terminal hydro-phobic domain responsible for oligomerization and for anchoring phospholamban in the membrane. The N-terminal domain is a basic amphiphilic a-helix, which resembles the calmodulin-binding domain of many proteins (Chiesi efa/., 1991). Phospholamban is phosphorylated at serine-16 by cAK and cGK and at threonine-17 by Ca +/calmodulin-dependent protein 

EXPRESSION OF Ca2+ PUMPS AND PHOSPHOLAMBAN IN SMOOTH MUSCLE CELLS  

The analysis of mRNA levels in pig tissues revealed four classes of SERCA2-derived mRNAs. Class 1 (4.4 kb) encodes SERCA2a, whereas classes 2 (4.4 kb), 3 (8.0 kb), and 4 (5.6 kb) encode the SERCA2b isoform. These four mRNA classes present a tissue-specific dis- 

A major unresolved question concerns the sub-cellular localization of the SERCA2a and SERCA2b isozymes. If the tails of these isoforms would contain different targeting signals, their compartmentalized expression would create discrete regions of cytosolic 

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