Ss-bCNGa: a unique member of the bacterial cyclic nucleotide gated (bCNG) channel family that gates in response to mechanical tension

Abstract

Bacterial cyclic nucleotide gated (bCNG) channels are generally a nonmechanosensitive subset of the mechanosensitive channel of small conductance (MscS) superfamily. bCNG channels are composed of an MscS channel domain, a linking domain, and a cyclic nucleotide binding domain. Among bCNG channels, the channel domain of Ss-bCNGa, a bCNG channel from Synechocystis sp. PCC 6803, is most identical to Escherichia coli (Ec) MscS. This channel also exhibits limited mechanosensation in response to osmotic downshock assays, making it the only known full-length bCNG channel to respond to hypoosmotic stress. Here, we compare and contrast the ability of Ss-bCNGa to gate in response to mechanical tension with Se-bCNG, a nonmechanosensitive bCNG channel, and Ec-MscS, a prototypical mechanosensitive channel. Compared with Ec-MscS, Ss-bCNGa only exhibits limited mechanosensation, which is most likely a result of the inability of Ss-bCNGa to form the strong lipid contacts needed for significant function. Unlike Ec-MscS, Ss-bCNGa displays a mechanical response that increases with protein expression level, which may result from channel clustering driven by interchannel cation-π interactions.

Nonpolar residues in the presumptive pore‐lining helix of mechanosensitive channel MSL10 influence channel behavior and establish a nonconducting function

“…The number of predicted transmembrane domains and the structure of N and C termini are highly variable. The channel behavior and physiological function of multiple Ec MscS homologs from other bacterial species, archaea, fission yeast, green algae, and land plants have been reported (Çetiner et al., ; Hamilton et al., ; Kloda & Martinac, ; Lee et al., ; Maksaev & Haswell, ; Malcolm et al., ; Nakayama, Fujiu, Sokabe, & Yoshimura, ; Nakayama, Yoshimura, & Iida, , ). These channels are all mechanically gated and generally function in hypoosmotic stress relief, but have a range of conductances and ion channel selectivities and play different physiological and developmental roles.…”

The mechanosensitive channel of small conductance (MscS) functions as a Jack-In-The Box

“…Gain of function analysis was carried out as previously described [32]. A single colony was used to inoculate an overnight culture in LB Broth supplemented with ampicillin (100µg/mL), the overnight culture was subsequently used to inoculate (1:75) a culture in LB Broth with ampicillin.…”

Heteromultimerization of Prokaryotic Bacterial Cyclic Nucleotide-Gated (bCNG) Ion Channels, Members of the Mechanosensitive Channel of Small Conductance (MscS) Superfamily

“…While this suggested to us that bCNG channels might exist as heteromultimeric assemblies, it was also possible that these bacteria contained multiple discrete homomeric bCNG channels or that one of these genes was simply not expressed under normal growth conditions. Although homomeric assemblies of bCNG subunits from some bacteria containing multiple bCNG genes are functional, 3,4 we demonstrate here that some bCNG channels likely exist in vivo as heteromultimers. To assess the ability of these channels to form complex assemblies, we have examined the ability of different bCNG subunits to assemble at a molecular level using homology modeling and molecular dynamics (MD) simulations, at the protein level using pull-down assays, and at the organismal level using quantitative real-time polymerase chain reaction (qRT-PCR) analysis.…”