Enables identical protein binding activity and protein dimerization activity. Involved in several processes, including activation of cysteine-type endopeptidase activity; positive regulation of cytokine production; and regulation of defense response. Acts upstream of or within several processes, including defense response to Gram-positive bacterium; positive regulation of macromolecule metabolic process; and regulation of autophagy. Located in cytosol; extracellular region; and nucleus. Part of inflammasome complex. Is expressed in several structures, including alimentary system; brain; heart; hemolymphoid system gland; and urinary system. Orthologous to human PYCARD (PYD and CARD domain containing).