importins การใช้

• By releasing importins, RanGTP activates these factors and therefore promotes the assembly of the mitotic spindle.
• Transportin-1 is thought to use the same principal mechanism to carry out nuclear transport as other Importins.
• Whereas importins depend on RanGTP to dissociate from their cargo, exportins require RanGTP in order to bind to their cargo.
• Importins release cargo upon binding to RanGTP, while exportins must bind RanGTP to form a ternary complex with their export cargo.
• Karyopherins, or importins, are cytoplasmic proteins that recognize NLSs and dock NLS-containing proteins to the nuclear pore complex.
• Protein that must be imported to the nucleus from the cytoplasm carry nuclear localization signals ( NLS ) that are bound by importins.
• Those karyopherins that mediate movement into the nucleus are also called importins, whereas those that mediate movement out of the nucleus are called exportins.
• Karyopherins, which may act as importins or exportins are part of the Importin-? super-family which all share a similar three-dimensional structure.
• Moreover, RanGTP promotes spindle assembly by mechanisms similar to mechanisms of nuclear transport : the activity of spindle assembly factors such as NuMA and TPX2 is inhibited by the binding to importins.
• Ran is in a different conformation depending on whether it is bound to GTP or GDP . In its GDP bound state, Ran is capable of binding karyopherins ( importins and exportins ).
• The ability of importins and exportins to transport their cargo is regulated by GTPases, enzymes that Ran, which can bind either GTP or GDP ( guanosine diphosphate ), depending on whether it is located in the nucleus or the cytoplasm.
• Although small molecules can enter the nucleus without regulation, macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit . " Cargo " proteins that must be translocated from the cytoplasm to the nucleus contain short amino acid sequences known as nuclear localization signals, which are bound by importins, while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins.
• Although small molecules can enter the nucleus without regulation, macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit . " Cargo " proteins that must be translocated from the cytoplasm to the nucleus contain short amino acid sequences known as nuclear localization signals, which are bound by importins, while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins.