Stress-induced Membrane Insertion at the β-Barrel Assembly Machinery Complex Regulates BepA Metalloprotease Activity
Abstract
Proteases must be tightly regulated to prevent uncontrolled degradation, yet the mechanisms ensuring such control remain poorly understood. Members of the widespread M48 metalloprotease family are kept inactive by an autoinhibitory plug that blocks catalytic water activation, but how this plug is released was unknown. Here, using genetic, biochemical and cryo-EM approaches, we discover the activation mechanism of BepA, a quality-control protease that preserves outer membrane integrity by surveilling the β-barrel assembly machinery (BAM) in Gram-negative bacteria. Our cryo-EM analysis of BepA engaged with a stalled BAM-substrate assembly complex revealed that a flexible, unstructured α6-lid covering the active site in the latent protein functions as a molecular harpoon, inserting into the outer membrane when a substrate stalls at BAM and thereby docking BepA at the complex. This membrane anchoring promotes displacement of the autoinhibitory plug and unlocks protease activity precisely where and when it is needed. Thus, a dual enzyme activation mechanism is coupled to membrane association under stress, ensuring that BepA remains inactive until properly localized. Our findings reveal how membranes themselves can license protease activation, a principle that may extend beyond M48 metalloproteases.
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BibTeX
@misc{voedts2026stressinduced,
title = {{Stress-induced Membrane Insertion at the β-Barrel Assembly Machinery Complex Regulates BepA Metalloprotease Activity}},
author = {Henri Voedts and Phuong Chi Nguyen and Van-Son Nguyen and Pauline Leverrier and Bogdan I. Iorga and Seung Hyun Cho and Han Remaut and Jean-François Collet},
howpublished = {HAL},
year = {2026},
month = jul,
doi = {10.64898/2026.07.01.735768},
url = {https://hal.science/hal-05786973v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Stress-induced Membrane Insertion at the β-Barrel Assembly Machinery Complex Regulates BepA Metalloprotease Activity
AU - Henri Voedts
AU - Phuong Chi Nguyen
AU - Van-Son Nguyen
AU - Pauline Leverrier
AU - Bogdan I. Iorga
AU - Seung Hyun Cho
AU - Han Remaut
AU - Jean-François Collet
PY - 2026
DA - 2026/07/01
PB - HAL
DO - 10.64898/2026.07.01.735768
UR - https://hal.science/hal-05786973v1
AB - Proteases must be tightly regulated to prevent uncontrolled degradation, yet the mechanisms ensuring such control remain poorly understood. Members of the widespread M48 metalloprotease family are kept inactive by an autoinhibitory plug that blocks catalytic water activation, but how this plug is released was unknown. Here, using genetic, biochemical and cryo-EM approaches, we discover the activation mechanism of BepA, a quality-control protease that preserves outer membrane integrity by surveilling the β-barrel assembly machinery (BAM) in Gram-negative bacteria. Our cryo-EM analysis of BepA engaged with a stalled BAM-substrate assembly complex revealed that a flexible, unstructured α6-lid covering the active site in the latent protein functions as a molecular harpoon, inserting into the outer membrane when a substrate stalls at BAM and thereby docking BepA at the complex. This membrane anchoring promotes displacement of the autoinhibitory plug and unlocks protease activity precisely where and when it is needed. Thus, a dual enzyme activation mechanism is coupled to membrane association under stress, ensuring that BepA remains inactive until properly localized. Our findings reveal how membranes themselves can license protease activation, a principle that may extend beyond M48 metalloproteases.
ER -