| Phospholamban (PLN) and sarcolipin (SLN) are two single pass membrane proteins that regulate Ca2+ ATPase (SERCA), an ATP-driven pump that translocates calcium ions into the lumen of the sarcoplasmic reticulum initiating muscle relaxation. Both proteins bind SERCA through intramembrane interactions, impeding calcium translocation. While post-translational phosphorylation of PLN at Ser-16 and/or Thr-17 reestablishes calcium flux, the regulatory mechanism of SLN remains elusive. SERCA has been crystallized in several different states along the enzymatic reaction coordinates, providing remarkable mechanistic information; however, the lack of high-resolution crystals in the presence of PLN and SLN limits the current understanding of the regulatory mechanism. This thesis summarizes the progress towards understanding the SLN and PLN complexes with SERCA using a hybrid structural approach combining solution and solid-state nuclear magnetic resonance (NMR) methodologies. These results further the understanding of the calcium translocation process, and are the basis for designing new therapeutic approaches to ameliorate muscle malfunctions. |
