MPF, or mitosis-promoting factor, consists of two important cell cycle regulatory proteins called .

a. tubulin and kinetochorin
b. cyclin and cyclin-dependent kinase (CDK)
c. actin and myosin
d. rubisco and ATP synthase

B) cyclin and cyclin - dependant kinase (CDK)

Explanation: MPF also known as mitosis promoting factor is the cyclin-CDK complex, It stimulates the mitotic and meiotic phases of the cell cycle. MPF promotes the entrance into mitosis (the M phase) from the G2 phase by phosphorylating multiple proteins needed during mitosis. MPF is activated at the end of G2 by a phosphatase, which removes an inhibitory phosphate group added earlier during the cycle.

MPF is composed of two subunits:

Cyclin-dependent kinase 1 (CDK1), the cyclin-dependent kinase subunit uses ATP to phosphorylate specific serine and threonine residues of target proteins.

Cyclin is a regulatory subunit. The cyclins helps to regulate the function of the kinase subunit with the appropriate substrate. The mitotic cyclins can be grouped as cyclins A & B. These cyclins have 9 residue sequence in the N-terminal region called the “destruction box”, which can be recognized by the ubiquitin ligase enzyme which destroys the cyclins when appropriate.

Answer is b.cyclin and cyclin-dependent kinase (CDK). Therefore,

MPF, or mitosis-promoting factor, consists of two important cell cycle regulatory proteins called cyclin and cyclin-dependent kinase (CDK).

Explanation:

Cyclin-dependent kinases belongs to protein kinases and they are meant for their role of regulatory cell cycle.

i think the answer is b.