Formation of ER-lumenal intermediates during export of Plasmodium proteins containing transmembrane-like hydrophobic sequences

ABSTRACT: REX3RQLSE:Pf332:C-S11:DSLE is exported and is diffusely localised in the red blood cell cytoplasm (Fig 3A). Mutation of the PEXEL sequence (REX3AQLSE:Pf332:C-S11:DSLE), results in the protein being retained in the parasite (Fig 3C), and addition of a C-terminal SDEL sequence (REX3RQLSE:Pf332:C-S11:SDEL) also leads to retention of the protein within the parasite (Fig 3B). Given that REX3RQLSE:Pf332:C-S11:SDEL is retained within the parasite, this indicates that the C-terminus of the protein is in the ER lumen. To determine the location of the N-terminal end of this ER-retained protein, it was purified for tryptic digestion and analysis by mass spectrometry. The most N-terminal peptides retrieved corresponded to N-acetylated and non-acetylated SEPVVEEQDLK and SEPVVEEQDLKK. These peptides correspond to the expected N-terminal sequence following PEXEL cleavage by Plasmepsin V, indicating that the N-terminus of this protein is also in the ER-lumen. These data indicate that both N- and C-terminal ends of REX3RQLSE:Pf332:C-S11:SDEL are located within the ER lumen and consequently that in the context of this protein, the putative transmembrane segment of Pf332 has a propensity to translocate into the ER lumen rather than integrate into the ER membrane.

INSTRUMENT(S): Orbitrap Eclipse, Synapt G2-S MS

ORGANISM(S): Plasmodium Falciparum

TISSUE(S): Blood

SUBMITTER: Georgina Charlton  

LAB HEAD: Konstantinos Thalassinos

PROVIDER: PXD036904 | Pride | 2023-03-28

REPOSITORIES: Pride