We review work characterizing MCUb in physiology and pathophysiology, led by the Rizzuto, Elrod, Belosludstev, Hajnóczky, and Mammucari groups, highlighting implications within cardiac function and arrhythmia, and survey potential post‐translational modifications within MCUb as an additional layer of regulation to this subunit. This evidence concerns the gene MCUB and cardiac arrhythmia.