Nicolai Xavier, Liang Yucheng, Ruaudel Florence, Narajczyk Magdalena, Czajkowski Robert, Rusconi Filippo, Arthur Michel, Shevchik Vladimir E
CNRS UMR 5240 Microbiologie Adaptation et Pathogénie, Université Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France.
Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France.
Commun Biol. 2025 Jul 18;8(1):1071. doi: 10.1038/s42003-025-08488-9.
Gram-negative (diderm) bacteria possess a multilayered envelope comprising an inner membrane, a thin peptidoglycan (PG) layer and an outer membrane. In Escherichia coli and certain other γ-proteobacteria, including Dickeya dadantii, Braun lipoprotein, Lpp, covalently tethers the outer membrane to PG. Here, we show that in D. dadantii an inner membrane protein, OutB, is covalently attached to PG by the same catalytic mechanism as Lpp. Specifically, two L,D-transpeptidases, Ldt03 and Ldt84, catalyze protein attachment with a preference for muropeptide monomers and dimers, respectively. By altering the Lpp length, we show that the extended Lpp+21 enhances OutB attachment to PG, whereas the truncated LppΔ21 reduces it. Furthermore, we show that the PG-anchoring sequence of OutB tolerates substantial amino acid substitutions and allows PG-tethering of a periplasmic reporter protein, suggesting that other periplasmic and/or membrane proteins may also be tethered to PG in proteobacteria.
革兰氏阴性（双膜）菌具有多层包膜，包括内膜、一层薄的肽聚糖（PG）层和外膜。在大肠杆菌和某些其他γ-变形菌中，包括达旦氏果胶杆菌，布劳恩脂蛋白（Lpp）将外膜与PG共价连接。在此，我们表明在达旦氏果胶杆菌中，一种内膜蛋白OutB通过与Lpp相同的催化机制与PG共价连接。具体而言，两种L,D-转肽酶Ldt03和Ldt84分别催化蛋白连接，且分别偏好于肽聚糖单体和二聚体。通过改变Lpp的长度，我们表明延长的Lpp+21增强了OutB与PG的连接，而截短的LppΔ21则降低了这种连接。此外，我们表明OutB的PG锚定序列能够耐受大量氨基酸替换，并允许周质报告蛋白与PG连接，这表明在变形菌中其他周质和/或膜蛋白也可能与PG连接。
