In some cells, certain proteins are produced in large quantities.
For example, the observation of glands secreting certain hormones of a protein nature (which are released into the blood to act on other organs of the same organism) shows, in certain places, a row of ribosomes reading the same messenger RNA. Thus large amounts of the same protein are produced.
The set of ribosomes, acting along one mRNA, is called polyribosomes.
Possible protein destinations
The mRNA, leaving the nucleus can follow two destinations:
- Be translated into the ribosomes of the rough endoplasmic reticulum - and this protein will be exported out of the cell through the Golgi and out through vesicle-shaped exocytosis,
- Or it will be translated into free ribosomes in the cytoplasm - this protein will then remain inside the cell, performing some important function. Ex. Inside the Golgi, or free in the cytoplasm.
Protein synthesis in the cell nucleus?
At the nucleus of all eukaryotic cells, RNA production takes place by molding a strand of DNA. Then the RNA undergoes some changes and goes to the cytoplasm where it associates with ribosomes for protein formation. Protein synthesis (translation) was believed to occur only in the cytoplasm, but a recent paper published in the prestigious journal Science has shown that the elements necessary for translation associate in the nucleus, where proteins would be formed. In addition, the researchers found that the structures responsible for translation are active in the cell nucleus.