Basis of differentiation

Cyclins

Cyclin dependent kinases

Definition

Cyclins are regulatory molecular proteins involved in the cell cycle that have no enzymatic function on their own

Cyclin dependent kinases are catalytic proteins involved in the cell cycle that possess enzymatic function after activation by cyclins

Molecular weight

45 kDA to 87 kDa

34 kDa to 40 kDa

Expression

Expressed at specific stages of the cell cycle in

Expressed continuously throughout the cell cycle 

Function

Cyclins bind to CDKs in order to activate them and create maturation promoting factors that phosphorylate target proteins 

CDKs are the catalytic molecules responsible for phosphorylating target proteins which drive cell cycle progression. They phosphorylate wide ranges of substrates to facilitate events of the cell cycle