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Other proteins of various functions have also been experimentally inhibited of the NES signal such as the cyto-skeletal protein actin, which functions include cell motility and growth. The use of LBM as a NES inhibitor proved successful for actin resulting in accumulation of the protein within the nucleus, concluding universal functionality of ...
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 Ran small G-protein .
Nuclear pores are found in the nuclear envelope that surrounds the cell nucleus in eukaryotic cells. The nuclear envelope is studded by a great number of nuclear pores that give access to various molecules, to and from the nucleoplasm and the cytoplasm. Small molecules can diffuse easily but other larger molecules need to be transported across. [1]
Nucleoporins are a family of proteins which are the constituent building blocks of the nuclear pore complex (NPC). [1] The nuclear pore complex is a massive structure embedded in the nuclear envelope at sites where the inner and outer nuclear membranes fuse, forming a gateway that regulates the flow of macromolecules between the cell nucleus and the cytoplasm.
Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the cell. [ 1 ] [ 2 ] [ note 1 ] Proteins can be targeted to the inner space of an organelle , different intracellular membranes , the plasma membrane , or to the exterior of the cell via secretion .
The portion of the membrane proteins that are attached to the lipid bilayer (see annular lipid shell) consist mostly of hydrophobic amino acids. [13] Membrane proteins which have hydrophobic surfaces, are relatively flexible and are expressed at relatively low levels. This creates difficulties in obtaining enough protein and then growing crystals.
In order to transport cargo into the nucleus, importin-β must associate with the nuclear pore complexes. It does this by forming weak, transient bonds with nucleoporins at their various F G (Phe-Gly) motifs. Crystallographic analysis has shown that these motifs bind to importin-β at shallow hydrophobic pockets found on its surface. [10]
A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain.TMDs may consist of one or several alpha-helices or a transmembrane beta barrel.Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in TMDs are often hydrophobic, although proteins such as membrane pumps and ion channels can contain polar residues.