9C5A

AP-3 Arf1 dimeric interface, focused refinement

9C5A の概要

• エントリーDOI: 10.2210/pdb9c5a/pdb
• EMDBエントリー: 45207 45208 45209 45210 45211 45212 45213 45214
• 分子名称: AP-3 complex subunit beta-1, AP-3 complex subunit mu-1, ADP-ribosylation factor 1, ... (6 entities in total)
• 機能のキーワード: adaptor protein complex, endosomal trafficking, lysosomal trafficking, protein transport, ap complex, transport protein
• 由来する生物種: Homo sapiens (human); 詳細
• タンパク質・核酸の鎖数: 8
• 化学式量合計: 293954.68

構造登録者

Begley, M.C.,Baker, R.W. (登録日: 2024-06-06, 公開日: 2024-12-18, 最終更新日: 2025-03-05)

主引用文献

Begley, M.,Aragon, M.,Baker, R.W.
A structure-based mechanism for initiation of AP-3 coated vesicle formation.
Proc.Natl.Acad.Sci.USA, 121:e2411974121-e2411974121, 2024

PubMed Abstract: Adaptor protein complex-3 (AP-3) mediates cargo sorting from endosomes to lysosomes and lysosome-related organelles. Recently, it was shown that AP-3 adopts a constitutively open conformation compared to the related AP-1 and AP-2 coat complexes, which are inactive until undergoing large conformational changes upon membrane recruitment. How AP-3 is regulated is therefore an open question. To understand the mechanism of AP-3 membrane recruitment and activation, we reconstituted human AP-3 and determined multiple structures in the soluble and membrane-bound states using electron cryo-microscopy. Similar to yeast AP-3, human AP-3 is in a constitutively open conformation. To reconstitute AP-3 activation by adenosine di-phosphate (ADP)-ribosylation factor 1 (Arf1), a small guanosine tri-phosphate (GTP)ase, we used lipid nanodiscs to build Arf1-AP-3 complexes on membranes and determined three structures showing the stepwise conformational changes required for formation of AP-3 coated vesicles. First, membrane recruitment is driven by one of two predicted Arf1 binding sites, which flexibly tethers AP-3 to the membrane. Second, cargo binding causes AP-3 to adopt a fixed position and rigidifies the complex, which stabilizes binding for a second Arf1 molecule. Finally, binding of the second Arf1 molecule provides the template for AP-3 dimerization, providing a glimpse into the first step of coat polymerization. We propose coat polymerization only occurs after cargo engagement, thereby linking cargo sorting with assembly of higher-order coat structures. Additionally, we provide evidence for two amphipathic helices in AP-3, suggesting that AP-3 contributes to membrane deformation during coat assembly. In total, these data provide evidence for the first stages of AP-3-mediated vesicle coat assembly.

PubMed: 39705307
DOI: 10.1073/pnas.2411974121

実験手法

ELECTRON MICROSCOPY (4.2 Å)