1.A.133.1.1
The Csx28 pore-forming protein of 177 aas with 1 N-terminal TMS and possibly a second moderately hydrkophhobic region between residues 100 - 140.  It transports ions and colapses the inner membrane potential (pmf) by allowing the free flow of ions, possiblly inorganic cations, across the membrane. It has an octomeric structure with a well ordered C-terminal domain (VanderWal et al. 2023). The pore diameter is ~ 10 Å; each protomer is a 4-helix bundle (α1 to α4) where α1 and α2 form the inner lining of the pore and the two C-terminal helices form the outer surface of the pore. Cas13b senses the viral transcript and signals to Csx28.