Nuclear import and export are typically studied in cells treated with mild deter
ID: 217298 • Letter: N
Question
Nuclear import and export are typically studied in cells treated with mild detergents under carefully controlled conditions so that the plasma membrane is freely permeable to proteins, but nuclear envelope remains intact. Because the cytoplasm leaks out, nuclei take up proteins only when the cell remnants are incubated with fresh cytoplasm as a source of critical soluble proteins. One common substrate for uptake studies is serum albumin that is cross-linked with nuclear localization signal (NLS and fused with fluorescent label such as fluorescein, so that it can be visualized via microscopy. + GTP GTP cytosol Ran Ran +importin importin What does the data show? Which components (Ran, GTP and Importin are required for nuclear import?)Explanation / Answer
According to data Ran + Importin in the bounded form,GTP are required for nuclear import of protein.
Nuclear import of proteins- nuclear protein present on cytosol having nuclear localization signal. This signal is recognized by NLS receptor i.e Importin. Importin in Ran-GTP form present in cytosol. It Recognizes NLS and binds to it, GTP converts into GDP form by GTPase activating factor (GAF).This process occurs at filaments of nuclear basket. Now cargo + importin + Ran-GDP enters nucleus. This is how nuclear protein is imported inside nucleus.
Inside nucleus Ran GDP is replaced by Ran- GTP form. Cargo is released and Importin along with GTP comes out in cytosol.
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