Unc-13 Homolog D (UNC13D)

UNC13D is a member of the UNC13 family, containing similar domain structure as other family members but lacking an N-terminal phorbol ester-binding C1 domain present in other Munc13 proteins. The protein appears to play a role in vesicle maturation during exocytosis and is involved in regulation of cytolytic granules secretion. Mutations in this gene are associated with familial hemophagocytic lymphohistiocytosis type 3, a genetically heterogeneous, rare autosomal recessive disorder. The protein contains 2 calcium-binding C2 domains and 2 Munc13 homology domains, but it lacks the N-terminal region containing a phorbol ester-binding C1 domain present in other Munc13 proteins, such as UNC13B. MUNC13-4 distributed between the cytosol and membrane fractions in permeabilized platelets.