Dictionary > Nucleoporin

Nucleoporin

Definition

noun
plural: nucleoporins
Any of the family of porins that make up the nuclear pore complex

Details

Overview

The cell nucleus is the organelle of the eukaryotes responsible for maintaining the integrity of DNA and for controlling cellular activities such as metabolism, growth, and reproduction by regulating gene expression. It is a double-membraned organelle and this double membrane is referred to as nuclear envelope (also called nuclear membrane, plasmalemma, sor karyotheca). The nuclear envelope surrounds most of the eukaryotic cell’s genetic material as opposed to the genetic material of the prokaryotes that is not membrane bound. The nuclear envelope is a lipid bilayer and has many perforations. These perforations are called nuclear pores. Each nuclear pore is formed by the nuclear pore complex, the assembly of nucleoporins.

Features

The nucleoporins are the protein units of the nuclear pore complex. They form the nuclear pore where biomolecules may pass through it. Thus, nucleoporins forming a pore when they aggregate into a complex aid in the transport of biomolecules into and out of the nucleus. There are at least 456 nucleoproteins that make up the nuclear pore complex. The resulting nuclear pore is octagonal in shape, measures about 9 nm in diameter and with a depth of about 200 nm, and spans the nuclear envelope.

Types

The nucleoporin family is comprised of proteins involved in the formation of the nuclear pore complex. The nucleoporin 62 is the most abundant type of nucleoporins. Other examples of nucleoporins are nucleoporin 35, nucleoporin 37, nucleoporin 43, nucleoporin 50, nucleoporin 54, nucleoporin 85, nucleoporin 88, nucleoporin 93, nucleoporin 98, nucleoporin 107, nucleoporin 133, nucleoporin 153, nucleoporin 155, nucleoporin 205, nucleoporin 210, etc. They are named according to their molecular weight in kilo Daltons. Many of them contain solenoid protein domains.

Common biological reactions

Common biological reactions

The presence of the nuclear envelope prevents the easy passage of large molecules (e.g. proteins and RNA) into and out of the nucleus. Although the nuclear envelope is perforated with nuclear pores, large molecules would still need a nuclear transport mechanism in order to enter and exit the nucleus. Small particles (< ~30-60 kDa), such as ions, can pass through the nucleus by passive transport. However, cargo proteins and RNAs that need to be transported require importins and exportins to enter and exit the nucleus, respectively. On one hand, the cargo binds with the importin in the cytoplasm, and then moved into the nucleus through the nuclear pore. On the other hand, the cargo binds with the exportin inside the nucleus, and then moved outside the nucleus via the nuclear pore. Nuclear transport needs energy to proceed. Thus, GTPases (e.g. Ran enzyme) help by hydrolyzing GTP (guanosine triphosphate) so that energy would be released in the process. The energy released would be used to dissociate the cargo from the importins and to bind the cargo to the exportins.

Biological functions

Nucleoporins serve as the structural unit of the nuclear pore complex that is involved in the entry and exit of biomolecules across the nuclear envelope. A nuclear pore complex can translocate about 60,000 protein molecules per minute.

Supplementary

Etymology

Abbreviation

  • NUP
  • Further reading

    See also


    © Biology Online. Content provided and moderated by Biology Online Editors



    You will also like...

    Oligodendrocyte and Schwann cell
    The Central Nervous System

    Myelin sheath is essential for a faster conductivity of signals. Know more about this feature of some neurons in the Cen..

    river
    Running Water Freshwater Communities

    This tutorial introduces flowing water communities, which bring new and dithering factors into the equation for possible..

    Plant Auxins
    Plant Auxins – Phototropism & Geotropism

    Plants produce hormones to regulate their growth. Auxins, for instance, influence plant growth. Know the role of auxin i..

    New Zealand - Biodiversity fauna
    New Zealand’s Biodiversity

    Find out more about New Zealand's unique biodiversity by exploring a range of different ecosystems and the key role of s..

    kinesin motor proteins transporting molecules across microtubules
    Movement of Molecules Across Cell Membranes

    Molecules move within the cell or from one cell to another through different strategies. Transport may be in the form of..

    Protein (illustration)
    Protein Variety

    The sequence of amino acids determines the type of protein. Protein is synthesized according to the sequence of nucleoti..

    Related Articles...

    No related articles found

    See all Related Topics