Machin Jonathan M, Ranson Neil A, Radford Sheena E
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
J Mol Biol. 2025 Jul 14;437(19):169346. doi: 10.1016/j.jmb.2025.169346.
The outer membrane (OM) of lipopolysaccharide (LPS) containing-diderm bacteria is crowded with outer membrane proteins (OMPs) that reside in a membrane that is relatively rich in protein and poor in lipid. As a consequence, extensive interactions between OMPs occur. Yet, how these interactions affect OMP function remains unexplored. Here, we examine the effect of OmpA on the activity of three different OMP enzymes, OmpLA (a phospholipase), PagP (a palmitoyltransferase) and OmpT (a protease). We show that OmpA-OmpT interactions enhance the activity of OmpT, and that this catalytic enhancement is mediated via their extracellular loops, an effect that is not observed with other common OMPs, including OmpF and OmpX. In contrast, OmpA specifically reduces the activity of PagP, while OmpLA activity shows no significant change. Possible interactions between the abundant E. coli OMPs (OmpA, OmpF/C, OmpT, OmpX, MipA) and all other E. coli OMPs were screened via Alphafold predictions, with the results suggesting that smaller OMPs are generally more promiscuous interactors, and identifying new interactions that may plausibly form in the OMP-rich islands in the OM. Together, the results identify a previously underappreciated role for specific OMP-OMP interactions in modulating protein function in the OM, and highlight how evolution may have exploited the high local concentrations of abundant OMPs in the OM to tune enzyme activity.
含有脂多糖（LPS）的双膜细菌的外膜（OM）中挤满了外膜蛋白（OMP），这些蛋白存在于一个蛋白质相对丰富而脂质相对较少的膜中。因此，OMP之间会发生广泛的相互作用。然而，这些相互作用如何影响OMP功能仍未得到探索。在这里，我们研究了OmpA对三种不同的OMP酶OmpLA（一种磷脂酶）、PagP（一种棕榈酰转移酶）和OmpT（一种蛋白酶）活性的影响。我们发现OmpA与OmpT的相互作用增强了OmpT的活性，并且这种催化增强是通过它们的细胞外环介导的，其他常见的OMP（包括OmpF和OmpX）没有观察到这种效应。相比之下，OmpA特异性地降低了PagP的活性，而OmpLA的活性没有显著变化。通过Alphafold预测筛选了丰富的大肠杆菌OMP（OmpA、OmpF/C、OmpT、OmpX、MipA）与所有其他大肠杆菌OMP之间可能的相互作用，结果表明较小的OMP通常是更混杂的相互作用分子，并确定了可能在OM中富含OMP的区域形成的新相互作用。总之，这些结果确定了特定的OMP-OMP相互作用在调节OM中蛋白质功能方面以前未被充分认识的作用，并突出了进化可能如何利用OM中丰富OMP的高局部浓度来调节酶活性。
