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Updated: May 12, 2026

Cholesterol Efflux Assay
Published on: March 6, 2012
Cholesterol-dependent enzyme activity of human TSPO1
Weihua Qiu1,2, Thi Kim Hoang Trinh1,2, Claudio Catalano1,2
1Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA 23298-0540.
None:
The amino acid sequence of the tryptophan-rich sensory proteins (TSPO) is substantially conserved throughout all kingdoms of life. Human mitochondrial TSPO1 (HsTSPO1) binds to porphyrins and steroids, although its interactions with these molecules remains unknown. HsTSPO1 is associated with numerous physiological and pathological disorders, but the underlying molecular mechanisms are unknown. Here, we disclose the finding of human mitochondrial TSPO as a cholesterol-dependent protoporphyrin IX oxygenase. The results of our biochemical characterization are consistent with structural data and evolutionary analysis. The dependence of HsTSPO1 activity on cholesterol may be the result of the coevolution of this membrane protein with the membrane system. Our study provides a molecular foundation for comprehending the various roles played by mitochondrial TSPO in normal physiological and pathological situations.
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