Psalmotoxin-1 (PcTx1) 40 aas (Diochot et al., 2007).  The Pi theraphotoxin Pc1a potently and selectively blocks the acid-sensing ion channel ASIC1a/ACCN2. The blockade is rapid and reversible. Psalmotoxin 1 loses its capacity to block ASIC1a/ACCN2 as soon as this subunit is associated with another member of the family (ASIC2a/ACCN1 or ASIC3/ACCN3). The toxin can distinguish between the two ASIC1/ACCN2 splice variants ASIC1a/ACCN2 and ASIC1b/ACCN2 (Chagot et al. 2004).  The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin.  The 3-D structure is known (Chagot et al. 2005). This "gating blocker" mainly regulate ASIC1a gating through hydrogen bonds, which can affect the relative positions of several key domains in ASIC1a, and a long-range conformational change path was determined, which is composed of beta1, beta2, beta10, alpha6, alpha7, beta11 and beta12 in ASIC1a (Yu et al. 2017).