Sarcolipin (SLN) is an integral membrane protein that is expressed in both 
skeletal and cardiac muscle, where it inhibits SERCA (calcium ATPase) by 
lowering its apparent Ca2+ affinity in a manner similar to that of its homologue 
phospholamban (PLN). We use solution NMR to map the structural changes occurring 
within SLN upon interaction with the regulatory target, SERCA, co-reconstituting 
the two proteins in dodecylphosphocholine (DPC) detergent micelles, a system 
that preserves the native structure of SLN and the activity of SERCA, with the 
goal of comparing these interactions with those of the previously studied 
PLN-SERCA complex. Our analysis of the structural dynamics of SLN in DPC 
micelles shows this polypeptide to be partitioned into four subdomains: a short 
unstructured N terminus (residues 1-6), a short dynamic helix (residues 7-14), a 
more rigid helix (residues 15-26), and an unstructured C terminus (residues 
27-31). Upon addition of SERCA, the different domains behave according to their 
dynamics, molding onto the surface of the enzyme. Remarkably, each domain of SLN 
behaves in a manner similar to that of the corresponding domains in PLN, 
supporting the hypothesis that both SLN and PLN bind SERCA in the same groove 
and with similar mechanisms.