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Targeting signals and subunit interactions in coated vesicle adaptor complexes
1Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, England.
The Journal of Cell Biology
|November 1, 1995
Summary
Cellular adaptor complexes target specific membranes. Researchers identified key protein regions and subunit interactions essential for directing these complexes, revealing how subunits cooperate for accurate membrane targeting.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Interactions
Background:
- Cells utilize distinct clathrin-coated vesicle adaptor complexes for plasma membrane and trans-Golgi network (TGN) functions.
- These complexes consist of specific subunit compositions, including alpha/gamma-adaptins, beta/beta'-adaptins, and AP50/AP17 or AP47/AP19.
Purpose of the Study:
- To identify the targeting signals within adaptor complexes responsible for membrane localization.
- To elucidate the roles of specific subunits in the assembly and targeting of adaptor complexes.
Main Methods:
- Construction of chimeric proteins between alpha- and gamma-adaptin NH2-terminal domains.
- Immunoprecipitation assays to assess subunit coassembly.
- Yeast two-hybrid system to investigate protein-protein interactions between adaptor subunits.
Main Results:
- Specific sequences (amino acids ~130-350) in the NH2-terminal domains of alpha- and gamma-adaptin were found essential for targeting.
- These regions dictate coassembly with either AP50/AP17 or AP47/AP19, suggesting their crucial role in targeting.
- Beta- and beta'-adaptins were not involved in this initial targeting event.
- Interactions between various adaptor subunits (beta/beta' with alpha/gamma, beta/beta' with AP50/AP47, alpha with AP17, gamma with AP19) were confirmed.
Conclusions:
- Adaptor protein targeting signals reside in their NH2-terminal domains and are critical for membrane specificity.
- The identified targeting signals influence the assembly of specific accessory subunits (AP50/AP17 or AP47/AP19).
- Adaptor subunits function in a coordinated manner to ensure the correct localization of clathrin-coated vesicle complexes to their designated cellular membranes.