Cortical patch protein involved in endocytosis. May serve as an adapter to link INP52 and INP53 to the cortical actin cytoskeleton. Interacts with CAP1, RVS167, SLA1, INP52 and INP53. The INP52 and INP53 C-terminal Sac1 domains are required for the binding with BSP1. Peripheral membrane protein in a PtdIns(4)P and PtdIns(4,5)P2 manner. Phosphorylated by CDC28. Present with 704 molecules/cell in log phase SD medium.