The Plasmodium Translocon of Exported proteins (PTEX) complex included Exp2 (283 aas; one N-terminal TMS plus 8 putative TM β-strands), Clp protease and ATPase (ClpB2). and translocon components, PTEX150 (993 aas with one N-terminal TMS and as many as 22 TM putative β-strands), pTEX88 (777 aas with one or two N-terminal α-helical TMSs and as many as 30 TM β-strandsm and thioredoxin-2 (Trx2; 157 aas, one N-terminal TMS). ClpB2 is an ATP-dependent protein unfoldase and chaparone that may energize substrate protein unfolding and export; it is not clear if the Clp protease is involved. 3-d structures are known for some components (AhYoung et al. 2015). It has been suggested that the Exp-2 protein serves as the channel for export (Mesén-Ramírez et al. 2016), and this has been demonstrated (Hakamada et al. 2016). EXP2 formed pores in bilayer lipid membranes with an inner diameter of approximately 3.5 nm. The pore consists of 10-12 EXP2 subunits (Hakamada et al. 2017), and the N-terminus of EXP2 plays a role in pore formation (Sanders et al. 2018). An additional component of the complex may be Pf113 (Miyazaki et al. 2021). EXP2, the transmembrane protein of a translocon from malaria parasites has pore-forming properties in the lipid bilayer and forms a nanopore with a diameter of 2.5 nm assembled from 7 monomers. Using the EXP2 nanopore allowed detection of poly-L-lysine (PLL) at a single-molecule level. The EXP2 nanopore has sufficient resolution to distinguish the difference in molecular weight between two individual PLL, long PLL (MW: 30,000-70,000) and short PLL (MW: 10,000) and thus functions as a peptide-detectable nanopore (Miyagi et al. 2021).
PTEX complex of Plasmodium falciparum
Hsp101 (Clp protease subunit)