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Figure 5.
Figure 5. Model for Golgi-specific targeting and localization of
TRAPP. The flat surface of mouse bet3, which is predominantly
positively charged, would interact with negatively charged polar
head groups of lipids. The landed bet3 protein could search for
its Golgi-specific partner protein in a two-dimensional fashion.
The secondary and firm attachment of bet3 to the Golgi occurs
via the insertion of the acyl chain of the partner protein into
the hydrophobic channel of bet3. In the beacon model, bet3 first
attaches to the Golgi and directs the recruitment of the other
TRAPP subunits. In the headlight model, the complex or a portion
of the complex is preassembled in the cytosol and directed to
the Golgi by the bet3 subunit. Secondary attachment to the Golgi
would occur via the acyl groups as described above. The
schematic drawing of the TRAPP complex does not reflect how
TRAPP components interact with each other in the complex, which
is as yet unknown.
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