BIO206H5 Lecture Notes - Lecture 20: Nuclear Localization Sequence, Nuclear Transport, Active Transport
Document Summary
***test only up to lecture 19b; only up to plasma membrane. Signal: 1-2 short sequences containing positive lys or arg amino acids. Nuclear localization signal, nls ppkkkrkv; a number of positively charged aas; in the body of the protein. Requires nuclear import receptor proteins (cytosolic); requires machinery. Interact with fibrils on they cytoplasmic side of the nucleur pore. Nuclear transport receptor bound by hydrogen bonds to prospective nuclear protein; interacts with fibrils which results in the opening of the pore. Release of the imported protein from the receptor is a catalyzed reaction; Another protein ran-gtp (gtp binding site on surface) has a higher affinity to the binding site than the protein so exchange reaction occurs. Ran-gtp is now bound to the receptor and it is competent to be exported from the nucleus to the cytoplasm. Ran-gtp also participates in the export of proteins. Ran protein cycles from nucleus to cytoplasm and back. Ran-gdp needs to get back to the nucleus.
