Raptor, also known as regulatory associated protein of mTOR, is a scaffold protein of approximately 150 kD that is highly expressed in skeletal muscle. Raptor functions as an essential scaffold for mTOR-catalyzed phosphorylation of 4EBP1 critical for TOR activity in vivo. Raptor is involved in nutrient-stimulated signaling to the downstream effector RPSKB1 and has been shown to negatively regulate the FRAP1 kinase under conditions of nutrient deprivation. Raptor/FRAP1 interactions are critical for the coordination of cell size and cell growth under different environmental conditions. The Raptor protein has been shown to interact with mTOR, 4EBP1, RPS6KB1 and FRAP1. The Poly6232 antibody recognizes human Raptor and has been shown to be useful for Western blotting.