This structure shows that two human recptor ACE2(angiotensin converting enzyme 2) bind to RBDs of two spike proteins.
The bottom brown disk is virus membrane, and the upper blue disk is human cellular membrane.
This is the first step of the infection of the coronavirus.
After the binding to the ACE2, the head S1 region of the spike is cleavaged and goes away,
and the viral membrane and the human membrane are fused, and the virus particle enters into the human cell.
human molecules
human ACE2 receptors
human cellular membrane