Medical Biochemistry Commons^™

Binding Between The Niemann–Pick C1 Protein And A Photoactivatable Cholesterol Analog Requires A Functional Sterol-Sensing Domain, Nobutaka Ohgami, Dennis C. Ko, Matthew Thomas, Matthew P. Scott, Catherine C. Y. Chang, Ta-Yuan Chang

Dartmouth Scholarship

Niemann-Pick type C (NPC) 1 protein plays important roles in moving cholesterol and other lipids out of late endosomes by means of vesicular trafficking, but it is not known whether NPC1 directly interacts with cholesterol. We performed photoaffinity labeling of intact cells expressing fluorescent protein (FP)-tagged NPC1 by using [(3)H]7,7-azocholestanol ([(3)H]AC). After immunoprecipitation, (3)H-labeled NPC1-GFP appeared as a single band. Including excess unlabeled sterol to the labeling reaction significantly diminished the labeling. Altering the NPC1 sterol-sensing domain (SSD) with loss-of-function mutations (P692S and Y635C) severely reduced the extent of labeling. To further demonstrate the specificity of labeling, we show that …