K13 copurified in a PfEMP1-immunoproteome enriched in proteostatic pathways that include the UPR, implicated in clinical artemisinin resistance. (A) Detection of PfEMP1 (arrow, left panel) and total protein content (right panel) captured by anti-ATS antibodies (but not in its absence at −1°) on covalently conjugated protein G beads. Molecular weight standards are in kDa. *Heavy IgG; **Light IgG. (B) Intensity properties of 2 replicate PfEMP1 immunoproteomes. (C) Distribution of proteins in the “503-proteome” comparing their abundance in each proteome expressed as a ratio (abundance ratio [AR] = abundance in Proteome 1/abundance in Proteome 2). X-axis: AR interval range; y-axis: number of proteins. (D) Hypergeometric analyses of 503-proteome and artemisinin-resistant transcriptome associated with clinical strains¹²  (for proteostasis enrichment and more detail, see supplemental Tables 2-4; Figure 3E-G). (E) Distribution of normalized intensity (ni; intensity divided by molecular weight) of the 207-proteome (AR = 0.5-1.99). Reactive oxidative stress complex components are BiP and PDI-11 (ni 5.17e8 and 1.2e7, respectively; supplemental Table 5). For detailed annotation and proteostasis enrichment, see supplemental Table 4 and supplemental Figure 3H-I. (F) Model integrating K13-PI3P tubules/vesicles (black-gray spheres based on findings of Figures 1 and 2 and supplemental Figures 1 and 2) and K13-PfEMP1 immunoproteome (green; based on findings in Figure 3; supplemental Figure 3) in proteostatic mechanisms of vesicular export and protein quality control and folding in the ER and cytoplasm (dotted circle). Experimental replicates, n = 2. Other organelles and key are as shown. HT, host targeting sequence; PEXEL, plasmodium export element; PNEP, PEXEL-negative proteins; PPM, parasite plasma membrane; PVM, parasitophorous vacuolar membrane; ROSC, reactive oxidative stress complex.