Investigating the role of YciM as an Adaptor Protein Regulating Lipopolysaccharide Synthesis in Escherichia coli

Abstract

The outer membrane (OM) of Gram-negative bacteria such as Escherichia coli displays a unique asymmetric organization of lipids, with phospholipids comprising the inner leaflet and lipopolysaccharides (LPS) forming the outer leaflet. This lipid organization is critical for the maintenance of OM integrity which protects the cell from toxic compounds such as detergents or antibiotics. Because LPS is integral to maintaining the OM defense, its production is tightly regulated within the cell, particularly at the first committed step of LPS biosynthesis, catalyzed by the enzyme LpxC. YciM is known to negatively regulate LPS levels by facilitating the proteolysis of LpxC via the FtsH protease. While it is known that YciM interacts with both FtsH and LpxC, how these interactions work is still not fully understood. This study aimed to further characterize the role of YciM within this pathway, and to gain further insight into how and where YciM interacts with its known binding partners, as well as to potentially discover any additional binding partners of YciM. Through this study, it was discovered that overexpression of yciM is toxic to cells. This is believed to be a result of too much degradation of LpxC, which lowers LPS levels and weakens the OM, and experiments in progress were to confirm this. Completion of this study will provide further insight into the careful regulation of LPS production, ultimately aiding in the understanding of OM biosynthesis. Additionally, further understanding of this pathway can offer additional targets for the development of new antibiotics.