RIMS-binding proteins (RIM-BPs) serve as adaptors during vesicle fusion and release by forming links between synaptic-vesicle fusion apparatuses and calcium channels. Specifically, RIM-BP2 (RIMS binding protein 2), also known as RBP2, is a 1,052 amino acid protein that links L-type Ca++ CP Alpha1D, N-type Ca++ CP Alpha1B, Rim1 and Rim2 during synaptic transmission. RIM-BP2 contains three fibronectin type-III domains and three SH3 domains, which are used to mediate binding to a proline-rich motifs. Existing as three alternatively spliced isoforms, RIM-BP2 is encoded by a gene that maps to human chromosome 12q24.33 and mouse chromosome 5 G1.3.