Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
Nat Commun. 2024 Aug 23;15(1):7246. doi: 10.1038/s41467-024-51628-8.
The translocation and assembly module (TAM) has been proposed to play a crucial role in the assembly of a small subset of outer membrane proteins (OMPs) in Proteobacteria based on experiments conducted in vivo using tamA and tamB mutant strains and in vitro using biophysical methods. TAM consists of an OMP (TamA) and a periplasmic protein that is anchored to the inner membrane by a single α helix (TamB). Here we examine the function of the purified E. coli complex in vitro after reconstituting it into proteoliposomes. We find that TAM catalyzes the assembly of four model OMPs nearly as well as the β-barrel assembly machine (BAM), a universal heterooligomer that contains a TamA homolog (BamA) and that catalyzes the assembly of almost all E. coli OMPs. Consistent with previous results, both TamA and TamB are required for significant TAM activity. Our study provides direct evidence that TAM can function as an independent OMP insertase and describes a new method to gain insights into TAM function.
易位和组装模块（TAM）被认为在外膜蛋白（OMP）的一小部分组装中起着关键作用，这是基于在体内使用 tamA 和 tamB 突变株进行的实验以及使用生物物理方法在体外进行的实验得出的。TAM 由一个 OMP（TamA）和一个通过单个α螺旋锚定在内膜上的周质蛋白组成（TamB）。在这里，我们在体外重新构建它到质体后检查了纯化的大肠杆菌复合物的功能。我们发现 TAM 催化四种模型 OMP 的组装几乎与β桶组装机（BAM）一样好，BAM 是一种通用的异源寡聚体，包含一个 TamA 同源物（BamA），并催化几乎所有大肠杆菌 OMP 的组装。与先前的结果一致，TamA 和 TamB 都需要 TAM 具有显著的活性。我们的研究提供了直接的证据，证明 TAM 可以作为独立的 OMP 插入酶发挥作用，并描述了一种新的方法来深入了解 TAM 的功能。
