Prokaryotic mechanosensitive channels mediate copper influx

Abstract

Copper is an essential micronutrient in all kingdoms of life, requiring a meticulous balance between acquisition and toxic overload. While copper import in eukaryotes has been investigated extensively, few prokaryotic copper importers have been identified, leading to the notion that cytoplasmic copper uptake is unnecessary in prokaryotes. Here we report that mechanosensitive channels are key players in prokaryotic copper import. Deletion of the gene encoding the Escherichia coli small mechanosensitive channel, _EcMscS, leads to significantly reduced copper influx. Conversely, overexpression of _EcMscS leads to increased copper influx, elevated intracellular copper content, and renders cells hypersensitive to copper. Furthermore, specific channel blockers and competing permeating ions inhibit _EcMscS copper conductance, lowering intracellular copper accumulation and alleviating copper hypersensitivity. These findings extend beyond E. coli, as other prokaryotic small mechanosensitive channels of bacterial and archaeal origin also facilitate copper influx. Taken together, these results uncover a previously unknown moonlighting function for mechanosensitive channels as a pathway for prokaryotic copper uptake.

Keywords: bacteria; copper; ion channels; mechanosensitive channels; membrane permeation; metal homeostasis; prokaryotes; transport.