Tripathi Ritu, Ayekpam Dylan, Kanaujia Shankar Prasad
Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India.
Arch Microbiol. 2025 Apr 2;207(5):107. doi: 10.1007/s00203-025-04308-0.
The maintenance of the lipid asymmetry (Mla) system plays a critical role in facilitating the transport of phospholipids between the inner and outer membranes of the Gram-negative bacteria. In E. coli, the system consists of six proteins: MlaA-OmpF/C complex (outer membrane), MlaC (periplasm), and MlaFEDB complex (inner membrane). Despite extensive research on the core proteins (MlaFED) of the Mla system, the occurrence of Mla components like MlaA, MlaB, and MlaC in diderm remains uncertain. Therefore, this gap presents a significant opportunity for further investigation, particularly regarding MlaC, which serves as the sole mobile component of the Mla system. This has led to the identification of multiple copies of MlaC in 63 distinct genera of Proteobacteria and related phyla. Interestingly, amongst these genera, the genetic arrangements of the mla operon were observed to be varying and, thus, were further categorized into four distinct groups. The variations among the genetic organization of the mla operons suggest their evolution through various processes, such as duplications, losses, rearrangements, and fusions. Further, the results of this study highlight the MlaC's substrate promiscuity, illuminating new avenues for the Mla system.
脂质不对称性维持（Mla）系统在促进革兰氏阴性菌内膜和外膜之间磷脂的转运中起着关键作用。在大肠杆菌中，该系统由六种蛋白质组成：MlaA - OmpF/C复合物（外膜）、MlaC（周质）和MlaFEDB复合物（内膜）。尽管对Mla系统的核心蛋白（MlaFED）进行了广泛研究，但MlaA、MlaB和MlaC等Mla组分在双膜细菌中的存在情况仍不确定。因此，这一空白为进一步研究提供了重要机会，特别是对于作为Mla系统唯一移动组分的MlaC。这导致在63个不同的变形菌门属和相关门中鉴定出多个MlaC拷贝。有趣的是，在这些属中，观察到mla操纵子的基因排列各不相同，因此进一步分为四个不同的组。mla操纵子基因组织的差异表明它们通过各种过程进化，如重复、缺失、重排和融合。此外，本研究结果突出了MlaC的底物混杂性，为Mla系统开辟了新的研究途径。
