This is the N-terminal domain of Niemann-Pick C1 family proteins. This family of proteins mediates transport of cholesterol from the intestinal lumen to enterocytes. This domain contains a cholesterol-binding pocket [1-2].

1: Evidence for a Niemann-pick C (NPC) gene family: identification and characterization of NPC1L1. Davies JP, Levy B, Ioannou YA; Genomics. 2000;65:137-145. PMID:10783261

2: The structure of the NPC1L1 N-terminal domain in a closed conformation. Kwon HJ, Palnitkar M, Deisenhofer J; PLoS One. 2011;6:e18722. PMID:21525977