Sandbox 125: Difference between revisions
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The PY-NLS of 2H4M contains a hydrophobic rather than a basic N-terminal motif. Hydrophobic interactions at the N-terminal motif of the PY-NLS include: | The PY-NLS of 2H4M contains a hydrophobic rather than a basic N-terminal motif. Hydrophobic interactions at the N-terminal motif of the PY-NLS include: | ||
<scene name='37/372725/Kapb2_hydrophobic_interactions/ | <scene name='37/372725/Kapb2_hydrophobic_interactions/4'>Phe273, Gly274, Pro275 and Met276 of the NLS with Trp730 and Ile773 of KapB2</scene>. Interactions of the C-terminal RX2-5PY motif of the NLS include: <scene name='37/372725/Kapb2_hydrophobic_interactions/6'>Arg284 of the NLS with Glu509 and Asp543 of KapB2.</scene>; <scene name='37/372725/Kapb2_hydrophobic_interactions/9'>Pro288 and Tyr289 of the NLS with Ala380, Ala381, Asp384, Leu419, Ile457, Trp460 and Arg464 of KapB2.</scene> | ||
Upon binding Kapβ2,the NLS gains structure, conforms to and makes contact with the internal surface of the KapB2 C-terminal arch. | Upon binding Kapβ2,the NLS gains structure, conforms to and makes contact with the internal surface of the KapB2 C-terminal arch. | ||
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<StructureSection load='1qbk' size='500' side='left' caption='KapB2 with Ran (PDB entry [[1qbk]])' scene=''> | <StructureSection load='1qbk' size='500' side='left' caption='KapB2 with Ran (PDB entry [[1qbk]])' scene='37/372725/1qbk/1'> | ||
=='''How does Kapβ2 release its cargo? '''== | =='''How does Kapβ2 release its cargo? '''== | ||
Ran is a GTP binding protein that is found in greater concentrations in the nucleus than in the cytoplasm. In the nucleus Ran Guanine Nucleotide Exchange Factor (ranGEF) is a protein that catalyzes the dissociation of GDP from Ran and subsequent phosphorylation. Ran-GTP undergoes conformational changes that allow it to have a greater affinity for Kapβ2 than Ran-GDP. These conformational changes occur in Ran between residues 30-47 and residues 65-80. | |||
RanGTP has an overall positive charge allowing it to bind to the highly negative core of the N-terminal arch Kapβ2. There are two distinct regions of polar interaction between KapB2 and RanGTP. These regions of Kapβ2 are defined as the N Interface found within HR1-3, and the Central Interface found within HR6, HR7, 62-residue loop of HR8, HR13 and HR14. | |||
Polar interactions at the N Interface include Ser22, Arg31, Glu161, Asp 164 and Ser165 of KapB2, and Trp64, Val45, Arg110, and Arg106 of RanGTP. | |||
Polar interactions at the Central Interface include Asn271, Glu275, Glu278, Glu332, Glu333, Asp334, Arg336, His340, Glu363, Ile364, Asp366, Asp367, Ile370, Ser371, Trp373, Lys377, Asp639, Glu682 of KapB2 and Asn143, Lys141, Arg140, Asn154, Asn156, Lys159, Asp148, Tyr155, Lys127, Lys134, Lys132, Arg129, His139, Tyr 146, Gln145, Asn143, Arg140, and Lys127 of RanGTP. | |||
When RanGTP binds to Kapβ2 conformational changes occur within the N-terminal arch and within a long (62 residue) loop of HEAT repeat 8. It is the changes in the 62-residue loop (residues 311-373) that is important in the dissociation of the NLS. It is thought that the 62- residue loop binds into the NLS binding site thus releasing the NLS. | |||
</StructureSection> | </StructureSection> | ||