Cytochrome P450(CYP)17A1 is a dual-function monooxygenase with a critical role in the synthesis or many human steroid hormones The enzyme is an important target for Lrealment of breast and prostate cancers that proliferate in response to estrogens and androgens.Despite the cryslallographic structures available for CYP17A1.,no membrane-bound structural features of this enzyme at atomic level are available.Accumulating evidence has indicated that the interactions between bounded CYPs and membrane could contribute to the recruitment of lipophilic substrates.To this end,we have investigated the effects on structural characteristics in the presence of the membrane for CYP17A1.The MD simulation results demonstrate a spontaneous insertion process of the enzyme to the lipid.Two predominant modes of CYP17A1 in the membrane are captured,characterized by the depths of insertion and orientations of the enzyme to the membrane surface.The measured heme tilt angles show good consistence with experimental data thereby verifying the validity of the structural models.Moreover,conformational changes induced by the membrane might have impact on the accessibility of the active site to lipophilic substrates.The dynamics of internal aromatic gale formed by Trp220 and Phe224 are suggested to regulate tunnel opening motions.The knowledge of the membrane binding charactcristics could guide futureex pcrimcnlal and computational works on membrane-bound CYPs so that various investigations of CYPs in their natural,lipid environment rather than in artificially solttbilized forms may be achieved.