Ectopic Neo-Formed Intracellular Membranes in Escherichia coli: A Response to Membrane Protein-Induced Stress Involving Membrane Curvature and Domains

Abstract

Bacterial cytoplasmic membrane stress induced by the overexpression of membrane proteins at high levels can lead to formation of ectopic intracellular membranes. In this review, we report the various observations of such membranes in Escherichia coli, compare their morphological and biochemical characterizations, and we analyze the underlying molecular processes leading to their formation. Actually, these membranes display either vesicular or tubular structures, are separated or connected to the cytoplasmic membrane, present mono- or polydispersed sizes and shapes, and possess ordered or disordered arrangements. Moreover, their composition differs from that of the cytoplasmic membrane, with high amounts of the overexpressed membrane protein and altered lipid-to-protein ratio and cardiolipin content. These data reveal the importance of membrane domains, based on local specific lipid–protein and protein–protein interactions, with both being crucial for local membrane curvature generation, and they highlight the strong influence of protein structure. Indeed, whether the cylindrically or spherically curvature-active proteins are actively curvogenic or passively curvophilic, the underlying molecular scenarios are different and can be correlated with the morphological features of the neo-formed internal membranes. Delineating these molecular mechanisms is highly desirable for a better understanding of protein–lipid interactions within membrane domains, and for optimization of high-level membrane protein production in E. coli.

Structure and assembly of CAV1 8S complexes revealed by single particle electron microscopy

“…It is therefore possible that CAV1 may not need to assemble into stable discs to support h -caveolae formation. Indeed, ectopic overexpression of several different membrane proteins can generate intracellular membranes in E. coli , implying that several distinct molecular mechanisms may be involved ( 36 ). Thus, CAV1 could potentially drive membrane remodeling in this model system by more than one mechanism, depending on its organization within the membrane.…”

Engineering endogenous ABC transporter with improving ATP supply and membrane flexibility enhances the secretion of β-carotene in Saccharomyces cerevisiae

“…Therefore, sufficient ATP has to be supplied to the ABC transporter overexpressed strains. Thirdly, the overproduction of membrane proteins embedded in the cell membrane would increase the rigidity of the cell membrane and disturb its normal function, one consequence is decreasing cell growth and the transport capacity [21]. Maintaining the normal function of the cell membrane is therefore necessary to efficient export products, such as improving membrane fluidity [22].…”

Structure and assembly of CAV1 8S complexes revealed by single particle electron microscopy

“…More work will be required to determine exactly how Cav1 bends membranes to form h-caveolae and caveolae, and whether the same or different mechanisms are responsible for mammalian caveolae biogenesis and h-caveolae assembly. In this regard, it is interesting to note that ectopic overexpression of other membrane proteins can also generate intracellular membranes in E. coli, indicating multiple mechanisms may be at play in this process (33).…”