SERCA3 in platelets. SERCA3 is a multidomain calcium pump consisting of a transmembrane domains (blue), a phosphorylation domain (P, light green), a nucleotide-binding domain (N, green), and an actuator domain (A, purple). It functions as a calcium pump during SOCE in platelets. SOCE occurs when STIM1 detects depleted internal calcium stores (light blue) and stimulates entry of extracellular calcium into platelet cytosol via Orai1. SERCA3 and SERCA2b function to pump calcium into internal stores. tBHQ, 2,5-di-(tert-butyl)-1,4-benzohydroquinone. Professional illustration by Idoya Lahortiga, Somersault18:24.