Signal-induced proliferation-associated protein 1 is a protein that in humans is encoded by the SIPA1 gene. The product of this gene is a mitogen induced GTPase activating protein (GAP). It exhibits a specific GAP activity for Ras-related regulatory proteins Rap1 and Rap2, but not for Ran or other small GTPases. This protein may also hamper mitogen-induced cell cycle progression when abnormally or prematurely expressed. It is localized to the perinuclear region. Two alternatively spliced variants encoding the same isoform have been characterized to date. [provided by RefSeq].
GTPase activator for the nuclear Ras-related regulatory proteins Rap1 and Rap2 in vitro, converting it to the putatively inactive GDP-bound state.