Fig. 7
Models of SLC9C1 gating by voltage and cAMP. a Cartoon depicting that SpSLC9C1 is active only when the voltage enables its activity. The VSD could gate exchange activity by providing access for ions to their binding sites either by removing a physical gate or by enhancing the binding affinity for uploading (non-accessible). Alternatively, in the resting state, ions have access to their binding sites, but the rocking mechanism is locked (non-rocking); voltage unlocks the rocking motion and thus allows switching between outward- and inward facing conformations. b Chemotactic signaling pathway in sea urchin sperm. Chemoattractant binding results in cGMP production and CNGK channel opening. The subsequent hyperpolarization activates SLC9C1. Alkalinization and cAMP production cooperate to open the CatSper channel. The intimate interaction between the exchanger and the soluble adenylate cyclase SACY is illustrated
