A small molecule allosterically activates SecA dependent secretion

The Sec pathway is an essential protein secretion route for all organisms. In bacteria, the SecA ATPase peripherally associates with the SecYEG channel to form the translocase that mediates preprotein export. Activation of the translocase depends strictly on the synergy of signal peptide and mature domain binding. Thus, client selectivity, translocase activation and protein secretion are coupled by one mechanism. We show here that a previously identified small molecule (HSI#6) binds SecA, modulates its intrinsic dynamics and allosterically activates the translocase in the absence of clients. By uncoupling translocase activation from preprotein binding, HSI#6 transformed the translocase into a promiscuous nanomachine that lost client selectivity and secreted unfolded pre- mature- and cytoplasmic- proteins with high efficiency in vivo or in vitro. To our knowledge, HSI#6 is the first activator of the Sec pathway and might offer unique opportunities for the discovery of new antibacterials. A small molecule that binds on SecA uncouples activation of the translocase from preprotein binding, transforming the Sec translocase into a promiscuous nanomachine that lost client selectivity and secretes any unfolded protein in vivo or in vitro.