The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA).
The crystal structure of SERCA in the ADP- and Ca2+-bound state is shown. D351 (in red) is the residue phosphorylated during the movement of Ca2+ ions into the ER or SR. The three cytoplasmic domains, phosphorylation (P), nucleotide binding (N) and actuator (A) are labelled. ADP is shown in yellow and Ca2+ ions in green. Protein Data Bank (PDB) code 2ZBD, rendered using PDB Protein Workshop.