TY - JOUR TI - Edge-strand of BepA interacts with immature LptD on the β-barrel assembly machine to direct it to on- and off-pathways AU - Miyazaki, Ryoji AU - Watanabe, Tetsuro AU - Yoshitani, Kohei AU - Akiyama, Yoshinori A2 - Storz, Gisela A2 - Hong, Heedeok A2 - Hong, Heedeok A2 - Huang, Yihua VL - 10 PY - 2021 DA - 2021/08/31 SP - e70541 C1 - eLife 2021;10:e70541 DO - 10.7554/eLife.70541 UR - https://doi.org/10.7554/eLife.70541 AB - The outer membrane (OM) of Gram-negative bacteria functions as a selective permeability barrier. Escherichia coli periplasmic Zn-metallopeptidase BepA contributes to the maintenance of OM integrity through its involvement in the biogenesis and degradation of LptD, a β-barrel protein component of the lipopolysaccharide translocon. BepA either promotes the maturation of LptD when it is on the normal assembly pathway (on-pathway) or degrades it when its assembly is compromised (off-pathway). BepA performs these functions probably on the β‐barrel assembly machinery (BAM) complex. However, how BepA recognizes and directs an immature LptD to different pathways remains unclear. Here, we explored the interactions among BepA, LptD, and the BAM complex. We found that the interaction of the BepA edge-strand located adjacent to the active site with LptD was crucial not only for proteolysis but also, unexpectedly, for assembly promotion of LptD. Site-directed crosslinking analyses indicated that the unstructured N-terminal half of the β-barrel-forming domain of an immature LptD contacts with the BepA edge-strand. Furthermore, the C-terminal region of the β-barrel-forming domain of the BepA-bound LptD intermediate interacted with a ‘seam’ strand of BamA, suggesting that BepA recognized LptD assembling on the BAM complex. Our findings provide important insights into the functional mechanism of BepA. KW - M48 family peptidase KW - omp85 family KW - LPS KW - pbpa KW - YfgC JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -