Structure and function of the SLAC/SLAH anion channel family

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At the beginning of 2008 SLAC1, the first member of a small gene family in Arabidopsis, was identified. Lack of SLAC1 function prevented activation of guard cell anion channels. Since SLAC1 could not be functionally analysed yet in any heterologous expression system, the structure-function relationship of SLAC/SLAH family members remains unclear. The applicants recently succeeded to functionally express members of the SLAC/SLAH family. Based on the predicted primary structure of SLAC1 we analysed the membrane spanning domains and cytoplasmic N- and C-termini by using topology-sensitive reporters. Using molecular- and biochemical approaches the number of subunits required for channel function will be determined. Within the SLAC/SLAH anion channel family we identified two subtypes differing in anion permeability, susceptibility toward blockers, and gating. Via chimera between these subtypes and mutational analysis we will identify channel domains responsible for ion selectivity and voltage control. Based on functional studies with a set of SLAC/SLAH mutants combined with biochemical analysis with recombinant channel protein, a molecular model of the channel complex will be generated. The proposed working model will be validated and refined by testing model predictions via mutation analyses. Based on the model and high-throughput screens with a chemical library we will search for anion channel blockers of high-affinity and specificity. Taking advantage of the model-predicted channel’s 3D structure on one side and blocker chemistry on another, designed channel effectors will be generated. The latter will serve structure-function studies and represent new tools for testing anion channel physiology and may constitute the basis for new agrochemicals.