Figure : h-cisPT (cartoon) synthesizes long prenyl chains, inserting a prenyl chain (yellow beads) into the ER membrane (beads colored by element, with carbons in gray, oxygens in red, phosphorus in brown, and white omitted for clarity). The h-cisPT protein is heterodimeric, with prenyl synthesis and membrane association through the DHDDS (green cartoon) subunit. NgBR (blue cartoon) is necessary for proper function in-vivo but not catalytically active. cisPT proteins can synthesize prenyl chains at a variety of lengths, with short chains occupying the length of the active site, and longer chains reaching up to 20 or more prenyl units in length.