The raw data set used in this study was composed of 2,675 micrographs. Particles (257,378) were picked from motion-corrected and contrast transfer function (CTF)-estimated micrographs for subsequent classifications. After multiple rounds of 2D classification, the remaining 61,539 particles were subjected to several rounds of 3D classification. Initial 3D classification yielded four major classes, where the most populated one contained 49% of total particles. An initial 3D reconstruction without imposed symmetry resulted in a moderate resolution at 9.6 Å. With C2 symmetry imposed, subsequent 3D refinement focused on the LBD and TMD layer improved the density map, allowing a reconstruction at 7.6 Å resolution. An additional two iterations of 3D classification and refinement using updated map as the reference further improved the reconstruction. The resolution of the final cryo-EM density map was estimated to be 7.3 Å.