The Role of the C-terminal Coiled-coil in the Cellular Localization and in the Osmotic Stress Response of Transporter ProP
ProP of Escherichia coli (ProPEc) is an osmosensory transporter and an H+-osmolyte symporter. Disruption of the antiparallel coiled-coils of ProPEc and Agrobacterium tumefaciens ProP (ProPAt) elevated the osmolalities at which the transporters became active. Corynebacterium glutamicum ProP (ProPCg), which lacks the coiled-coil heptads, required a higher osmolality for activation than ProPEc and ProPAt. In this work, the ProP orthologue from Xanthomonas campestris (ProPXc) was expressed and characterized in E. coli. ProPXc lacks coiled-coils heptads and has higher sequence identity to ProPEc (51%) than ProPCg (37%). ProPXc was found active at a lower osmolality than ProPEc, which contradicts the previously established pattern. Previously, fluorophore-tagged ProPEc was found to localize in E. coli cells’ poles and septa in correlation to the proportion of phospholipid cardiolipin (CL). To corroborate these findings, GFPmut2 was fused to ProPEc. In this work, we found some indications of correlation between the localization pattern of ProPmut2A206K-ProPEc and CL.