Question

Which of the following proteins come together to form ‘maturation promoting factors’ or ‘M-phase factors’?
A) Cyclin
B) Cyclin-dependent kinase
C) G proteins
D) Cyclin and cyclin-dependent kinase
D) Cyclin-dependent kinase and G proteins

Answer 1

Hint: Maturation promoting factors (MPF) promotes the entrance into mitosis from the G2 phase. MPF is activated by a phosphatase, whose work is to remove a phosphate that was added before. The above mentioned are all some or the other types of proteins.

Complete answer:
Maturation-promoting factor (MPF) is a cell cycle control element able to cause metaphase when injected into amphibian oocytes or when incubated with nuclei in a cell-free system.

Proteins are a large, complex group of molecules that have various functions to perform in the human body. These are required for the structure, function as well as regulation of the body. Around 20 different amino acids leads to the formation of a protein.

Let us now explore every protein mentioned and get to our answer-
A) Cyclin- It is a group of proteins that controls the progression of a cell through the cell cycle by activating cyclin-dependent kinase or CDK enzyme.
B) Cyclin-dependent kinase- It regulates cell cycle, transcription, mRNA processing and the differentiation of nerve cells. CDK binds cyclin.
C) G proteins- It plays a role in the biological process. It shows its involvement during the signal transduction and signals amplification process. The function as molecular switches during signalling. It possesses three subunits- alpha, beta and gamma. One of the subunit i.e. Alpha is unique for each G- protein.
D) Cyclin and cyclin-dependent kinase- cyclin and cyclin-dependent kinase complex come together and forms the maturation promoting factors. Its function is to stimulate meiotic and mitotic phases of the cell cycle. These were first discovered in frog eggs.
E) Cyclin-dependent kinase and G proteins- Both performs various functions but are not involved in the formation of MPF.

Therefore the correct answer is option ‘D’.

Note:
- Maturation promoting factors were discovered by two different teams of researchers- one included Yoshiko Masui and Clement Market and the other was Dennis Smith and Robert Ecker.
- The purpose of MPF is to stimulate the mitosis phase and promote the maturation of oocytes in the egg cells.