SREBP cleavage-activating protein

Sterol regulatory element-binding protein cleavage-activating protein, also known as SREBP cleavage-activating protein or SCAP is a is_associated_with::protein that in humans is encoded by the SCAP is_associated_with::gene.

SCAP contains a is_associated_with::sterol-sensing domain (SSD) and seven WD domains. In cholesterol-depleted cells, this protein binds to is_associated_with::sterol regulatory element binding proteins (SREBPs) and mediates their transport from the ER to the is_associated_with::Golgi apparatus. The SREBPs are then proteolytically cleaved and stimulate is_associated_with::sterol biosynthesis.

Function
SCAP is a regulatory protein that is required for the is_associated_with::proteolytic cleavage of the sterol regulatory element-binding protein (SREBP). SCAP is an integral membrane protein located in the is_associated_with::endoplasmic reticulum (ER). One of the cytosolic regions of SCAP contains a is_associated_with::hexapeptide amino acid sequence, MELADL, that functions to detect cellular cholesterol. When cholesterol is present, SCAP undergoes a conformational change that prevents it from activating SREBP and cholesterol synthesis does not occur.

Structure
Scap has 8 transmembrane domains and both the N-terminal and C-terminal face the is_associated_with::cytoplasm. Also, it binds SREBP by a series of consecutive WD repeats on its C-terminus.