Question

True or False. If false explain why it is false and explain what is meant by all parts of the statement.

The nuclear localization is a post-translational modification.

Answer 1

Answer - False

Explanation - Nuclear transport refers to the mechanisms by which molecules move across the nuclear membrane of a cell. The entry and exit of large molecules from the cell nucleus is tightly controlled by the nuclear pore complexes (NPCs). Although small molecules can enter the nucleus without regulation,macromolecules such as RNA and proteins require association with transport factors known as nuclear transport receptors like karyopherins called importins to enter the nucleus and exportins to exit.

Protein that must be imported to the nucleus from the cytoplasm carry nuclear localization signals (NLS) that are bound by importins. An NLS is a sequence of amino acids that acts as a tag. They are diverse in their composition and most commonly hydrophilic, even few may be hydrophobic sequences too. Proteins, transfer RNA, and assembled ribosomal subunits are exported from the nucleus due to association with exportins, which bind signaling sequences called nuclear export signals (NES). The ability of both importins and exportins to transport their cargo is regulated by the small Ras related GTPase, Ran.

Post-translational modification (PTM) refers to the covalent and generally enzymatic modification  of proteins following protein biosynthesis. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product.