Molecular dynamics, docking and quantum calculations reveal conformational changes influenced by CYP271A amino acid mutations related to cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid disorder caused by a deficiency in CYP27A1, the first enzyme in the bile acid biosynthesis pathway. CYP27A1 catalyzes the 7α-hydroxylation of cholesterol, playing an important role in cholesterol homeostasis. CTX leads to progressive neurological dysfunction, including cognitive impairment, epilepsy, peripheral neuropathy, and movement disorders. Missense mutations in CYP27A1 disrupt its activity, particularly at the heme binding region and the adrenodoxin-binding site. This study examined the structural effects of seven-point mutations in CYP27A1 using molecular dynamic (MD) simulations. Both mutant and wild-type (WT) proteins were modeled to observe their structural behavior. Additionally, by combining MD simulations, docking, and quantum calculations cholesterol binding was studied in WT and mutant proteins. Results indicated that mutations altered cholesterol binding mode, preventing it from adopting the correct position in the catalytic site. The substrate access channel in mutants became wider, shallower, or closed. The interaction between the isopropyl group of cholesterol and the heme was found to be crucial for the hydroxylation capacity of CYP27A1, as this interaction was only present in the cholesterol-WT complex.