Triggered (Cisz et al., 2008, Lee et al., 2001, Olive et al., 2007). In the case of the YscP ruler model, it has been proposed that the secretion channel is wide enough to accommodate two proteins in an extended conformation (Wagner et al., 2009). This line of reasoning could also be extended to the sensor model. Here the sensor would be inserted into the secretion channel in an extended conformat