In previous studies we determine the crystal structure of Haemophilus TehA at 1.20 Å resolution. The following systematic bioinformatics analyses led the discoveries of a family of novel membrane proteins, which contain the recent identified anion channel SLAC1 in plant. The SLAC1 channel controls turgor pressure in the aperture-defining guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought or high levels of carbon dioxide. As the SLAC1 channel is the most characterized member in this protein family, this novel protein family was named as SLAC1 family.
The TehA structure is a symmetrical trimer composed from quasi-symmetrical subunits with a novel fold. Each subunit has ten transmembrane helices arranged from helical hairpin pairs to form a central five-helix transmembrane pore. An extremely conserved phenylalanine residue gates the pore. The high-resolution structure detail reveals the channel gate of TehA is restricted in an unusual high energetic conformation, due to the interaction with local residues. This finding indicates a novel gating mechanism of SLAC1 family channel. To address this question, we seek to find mutant channel with an open pore. A penta mutant may indicate an open pore conformation of the channel, as supported by large conductance in the electrophysiological measurement. Further work is on going to obtain structural information.