Kinases are complex tertiary-structure proteins. All protein kinases have a common structure that includes a catalytic domain, which is flanked by a regulatory domain and an effector domain.
The catalytic domain is made up of two lobes – the N-terminal lobe and the C-terminal lobe, which are connected by a hinge region. The hinge region is an active site for ATP and substrate binding. It also allows for conformational changes during the catalytic cycle.
On either side of the catalytic domain, there are two distinct domains - the regulatory domain and the effector domain. The regulatory domain binds to proteins that are responsible for regulating the enzyme's activity, while the effector domain binds to proteins that are present downstream of the enzyme’s action.