37IC

Doc2b-Munc13 complex with designed binder

Summary for 37IC

• Entry DOI: 10.2210/pdb37ic/pdb
• EMDB information: 78200
• Descriptor: Designed binder,Double C2-like domain-containing protein beta, Unc-13 homolog A (2 entities in total)
• Functional Keywords: doc2b, munc13, snares, neurotransmitter release, membrane binding, synaptic vesicle fusion, cytosolic protein
• Biological source: synthetic construct; More
• Total number of polymer chains: 2
• Total formula weight: 155456.17

Authors

Rastegar, C.,Han, Y.,Chen, Z.,Rizo, J. (deposition date: 2026-07-21, release date: 2026-11-11)

Primary citation

Rastegar, C.T.,Powell, J.,Wosztyl, A.,David, G.,Jaczynska, K.,Bai, X.C.,Han, Y.,Chen, Z.,Rizo, J.
Cryo-EM and NMR Reveal a Membrane-Gated Doc2B-Munc13-1 Complex and a Helical Doc2B-SNARE-Binding Interface.
Adv Sci, 2026

PubMed Abstract: Doc2s modulate neurotransmitter release through interactions with Munc13-1, SNAREs, lipids, and Ca, which involve the Doc2 C domains and Munc13-interacting domain (MID). However, it is unclear how these interactions are coupled, how Doc2s bind to Munc13-1, and how they bind to the SNAREs. Here we determined the cryo-electron microscopy structure of a Doc2B-Munc13-1 complex aided by an AI-designed Munc13-1 binder, revealing how Doc2B MID binds to a Munc13-1 hydrophobic pocket essential for opening syntaxin-1 and explaining why Doc2B inhibits SNARE assembly. NMR and fluorescence spectroscopy show that Doc2B MID binds lipids and that MID-lipid and MID-Munc13-1 interactions are mutually exclusive, suggesting that membrane binding helps release the inhibition of Munc13-1. NMR shows that Doc2B binds to the SNARE complex via two helices of CB. Based on these results and liposome fusion assays, we propose a working model whereby: 1. Doc2B MID-Munc13-1 interactions facilitate synergistic binding of both proteins to the plasma membrane, with the MID inhibiting Munc13-1. 2. Membrane binding facilitates MID-lipid interactions that transiently relieve the inhibition of Munc13-1, allowing SNARE complex assembly. 3. Doc2B binding to the SNARE complex inhibits neurotransmitter release but generates a primed state that mediates neurotransmitter release by an as-yet-unknown mechanism.

PubMed: 42973246
DOI: 10.1002/advs.78011

Experimental method

ELECTRON MICROSCOPY (2.94 Å)