Calcium-binding protein critical for proper photoreceptor cell maintenance and function. Plays a role in intracellular calcium homeostasis by decreasing ATP-induced calcium release. May be involved in the mechanotransduction process. Homodimer. Interacts with WHRN and MYO7A. Interacts with ITGA2B (via C-terminus cytoplasmic tail region) and ITGA7 (via C-terminus cytoplasmic tail region); the interactions are stabilized/increased in a calcium and magnesium-dependent manner. Colocalized with ITGA7 at the myotendinous junctions (MTJ) and at the neuromuscular junctions (NMJ). Localizes in the cuticular plate along and at the tip of the stereocilia of vestibular sensory hair cells. The binding of either calcium or magnesium significantly increases the structural stability of the protein in comparison to apo-CIB (calcium- and magnesium-free form).