7P3X

Homology model of the full-length AP-3 complex in a compact open conformation

Summary for 7P3X

• Entry DOI: 10.2210/pdb7p3x/pdb
• EMDB information: 13187
• Descriptor: AP-3 complex subunit delta, Y55_G0035830.mRNA.1.CDS.1, AP complex subunit sigma, ... (4 entities in total)
• Functional Keywords: adaptor protein, vesicle transport, ap-3, homology model, transport protein
• Biological source: Saccharomyces cerevisiae (Baker's yeast); More
• Total number of polymer chains: 4
• Total formula weight: 279465.74

Authors

Schubert, E.,Raunser, S. (deposition date: 2021-07-09, release date: 2021-09-29, Last modification date: 2024-07-17)

Primary citation

Schoppe, J.,Schubert, E.,Apelbaum, A.,Yavavli, E.,Birkholz, O.,Stephanowitz, H.,Han, Y.,Perz, A.,Hofnagel, O.,Liu, F.,Piehler, J.,Raunser, S.,Ungermann, C.
Flexible open conformation of the AP-3 complex explains its role in cargo recruitment at the Golgi.
J.Biol.Chem., 297:101334-101334, 2021

PubMed Abstract: Vesicle formation at endomembranes requires the selective concentration of cargo by coat proteins. Conserved adapter protein complexes at the Golgi (AP-3), the endosome (AP-1), or the plasma membrane (AP-2) with their conserved core domain and flexible ear domains mediate this function. These complexes also rely on the small GTPase Arf1 and/or specific phosphoinositides for membrane binding. The structural details that influence these processes, however, are still poorly understood. Here we present cryo-EM structures of the full-length stable 300 kDa yeast AP-3 complex. The structures reveal that AP-3 adopts an open conformation in solution, comparable to the membrane-bound conformations of AP-1 or AP-2. This open conformation appears to be far more flexible than AP-1 or AP-2, resulting in compact, intermediate, and stretched subconformations. Mass spectrometrical analysis of the cross-linked AP-3 complex further indicates that the ear domains are flexibly attached to the surface of the complex. Using biochemical reconstitution assays, we also show that efficient AP-3 recruitment to the membrane depends primarily on cargo binding. Once bound to cargo, AP-3 clustered and immobilized cargo molecules, as revealed by single-molecule imaging on polymer-supported membranes. We conclude that its flexible open state may enable AP-3 to bind and collect cargo at the Golgi and could thus allow coordinated vesicle formation at the trans-Golgi upon Arf1 activation.

PubMed: 34688652
DOI: 10.1016/j.jbc.2021.101334

Experimental method

ELECTRON MICROSCOPY (9.1 Å)