Rabphilin 3

Rab3-dependent synaptic vesicle Ca ²⁺-sensor

General Information

Rabphilin 3a is a putative effector protein for the low molecular weight GTP-binding protein rab 3. Rab 3 occurs in four isoforms (Rab 3a, b, c and d), all of which probably bind to rabphilin 3a when in the GTP-bound form.
Rabphilin 3a contains an N-terminal Zn²⁺-finger sequence that is essential for binding rab 3, and two C-terminal C2 - domains that may bind Ca²⁺. It does not have a transmembrane region.
Rabphilin 3a is primarily expressed in neurons where it is localized to synaptic vesicles. It is probably recruited to synaptic vesicles by rab 3a and 3c. The structure of rabphilin 3a and its interaction with rab 3 suggests that it may be a Ca²⁺ sensor on synaptic vesicles that is recruited to synaptic vesicles as a function of GTP by rab 3.