9TGQ

Cryo-EM structure of tail-engaged TamAB complex

This is a non-PDB format compatible entry.

Summary for 9TGQ

• Entry DOI: 10.2210/pdb9tgq/pdb
• EMDB information: 55908
• Descriptor: Translocation and assembly module subunit TamA, Translocation and assembly module subunit TamB (2 entities in total)
• Functional Keywords: escherichia coli k-12, membrane protein
• Biological source: Escherichia coli; More
• Total number of polymer chains: 2
• Total formula weight: 201780.08

Authors

Dong, H.,Tang, X.,Luo, Q.,Zerang, Z. (deposition date: 2025-12-02, release date: 2026-11-11)

Primary citation

Luo, Q.,Dong, X.,Zerang, Z.,Chen, Y.,Zhu, X.,Yang, L.,Zhang, Z.,Zhang, J.,Li, X.,Chen, H.,Ying, B.,Chang, S.,Zhou, J.,Dong, H.,Tang, X.
Mechanistic insights into TAM-mediated OMP assembly in Gram-negative bacteria.
Cell Rep, 45:117733-117733, 2026

PubMed Abstract: The β-barrel assembly machinery (BAM) is essential for outer membrane protein (OMP) biogenesis in Gram-negative bacteria and represents a validated target for antibiotic development. Its evolutionary relative, the translocation and assembly module (TAM), is thought to assemble OMPs but through a mechanism that remains poorly understood. Here, we present cryo-electron microscopy structures of Escherichia coli TamA and TamAB, capturing multiple conformational states. These structures reveal that the TamB C-terminal tail engages the TamA β-barrel to open its lateral gate, forming a transient hybrid β-interface and activating an extended AsmA-like periplasmic conduit that may facilitate substrate transport. Consistent with this mechanism, NanoLuc Binary Technology (NanoBiT)-based folding assays demonstrate that TamAB promotes OMP assembly more efficiently than TamA alone, with activity dependent on both lateral-gate opening and hybrid-interface formation. Together, our results define a substrate-mimetic priming mechanism that sets TAM apart from BAM and establish a structural framework for understanding OMP biogenesis.

PubMed: 42507553
DOI: 10.1016/j.celrep.2026.117733

Experimental method

ELECTRON MICROSCOPY (3.86 Å)